Generic Policy Information Model for Simplified Use of Policy Abstractions (SUPA)
draft-strassner-supa-generic-policy-info-model-03
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| Authors | John Strassner , Joel M. Halpern , Jason Coleman | ||
| Last updated | 2016-01-05 | ||
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draft-strassner-supa-generic-policy-info-model-03
Network Working Group J. Strassner
Internet Draft Huawei Technologies
Intended status: Standard Track J. Halpern
Expires: July 4, 2016 Ericsson
J. Coleman
Cisco Systems
January 4, 2016
Generic Policy Information Model for
Simplified Use of Policy Abstractions (SUPA)
draft-strassner-supa-generic-policy-info-model-03
Abstract
This document defines an information model for representing
policies using a common extensible framework that is independent
of language, protocol, repository, and the level of abstraction of
the content and meaning of a policy.
*************************************************************
* *
* Editor's note: this draft is still being changed by the *
* authors. However, it contains a significant rewrite and *
* update to reflect the new SUPA charter; hence, please *
* view this draft as an early pre-published version. An *
* updated version will follow soon. *
* *
*************************************************************
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Table of Contents
1. Overview ....................................................... 9
1.1. Introduction .............................................. 9
1.2. Changes Since Version -02 ................................ 11
2. Conventions Used in This Document ............................. 12
3. Terminology ................................................... 12
3.1. Acronyms .................................................. 12
3.2. Definitions ............................................... 12
3.2.1. Core Terminology ..................................... 12
3.2.1.1. Information Model .............................. 12
3.2.1.2. Data Model ..................................... 13
3.2.1.3. Abstract Class ................................. 13
3.2.1.4. Concrete Class ................................. 13
3.2.1.5. Container ...................................... 13
3.2.1.6. PolicyContainer ................................ 13
3.2.2. Policy Terminology ................................... 14
3.2.2.1. SUPAPolicyObject ............................... 14
3.2.2.2. SUPAPolicy ..................................... 14
3.2.2.3. SUPAPolicyClause ............................... 14
3.2.2.4. SUPAECAPolicyRule .............................. 14
3.2.2.5. SUPAMetadata ................................... 15
3.2.2.6. SUPAPolicyTarget ............................... 15
3.2.2.7. SUPAPolicySource ............................... 15
3.2.3. Modeling Terminology ................................. 16
3.2.3.1. Inheritance .................................... 16
3.2.3.2. Relationship ................................... 16
3.2.3.3. Association .................................... 16
3.2.3.4. Aggregation .................................... 16
3.2.3.5. Composition .................................... 17
3.2.3.6. Association Class .............................. 17
3.2.3.7. Multiplicity ................................... 17
3.2.3.8. Navigability ................................... 17
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3.3. Symbology ................................................ 18
3.3.1. Inheritance ......................................... 18
3.3.2. Association ......................................... 18
3.3.3. Aggregation ......................................... 19
3.3.4. Composition ......................................... 19
3.3.5. Association Class ................................... 19
3.3.6. Abstract vs. Concrete Classes ....................... 20
4. Policy Abstraction Architecture ............................... 21
4.1. Motivation ............................................... 22
4.2. SUPA Approach ............................................ 23
4.3. SUPA Generic Policy Information Model Overview............ 23
4.3.1. SUPAPolicyObject .................................... 25
4.3.2. SUPAPolicyStructure ................................. 26
4.3.3. SUPAPolicyComponentStructure ........................ 26
4.3.4. SUPAPolicyClause .................................... 26
4.3.5. SUPAPolicyComponentDecorator ........................ 27
4.4. The Design of the GPIM ................................... 28
4.4.1. Structure of Policies ............................... 28
4.4.2. Representing an ECA Policy Rule ..................... 30
4.4.3. Creating SUPA Policy Clauses ........................ 33
4.4.4. Creating SUPAPolicyClauses .......................... 35
4.4.5. SUPAPolicySources ................................... 37
4.4.6. SUPAPolicyTargets ................................... 39
4.4.7. PolicyMetadata ...................................... 39
4.4.7.1. Motivation ..................................... 39
4.4.7.2. Design Approach ................................ 40
4.4.7.3. Structure of SUPAPolicyMetadata ................ 43
4.5. Advanced Features ........................................ 43
4.5.1. Policy Grouping ..................................... 43
4.5.2. Policy Rule Nesting ................................. 43
5. GPIM Model .................................................... 44
5.1. Overview ................................................. 44
5.2. The Abstract Class "SUPAPolicy" .......................... 45
5.2.1. SUPAPolicy Attributes ............................... 46
5.2.1.1. The Attribute "supaObjectIDContent" ............ 46
5.2.1.2. The Attribute "supaObjectIDFormat" ............. 47
5.2.1.3. The Attribute "supaPolicyDescription" .......... 47
5.2.1.4. The Attribute "supaPolicyName" ................. 47
5.2.2. SUPAPolicy Relationships ............................ 48
5.2.2.1. The Relationship "SUPAHasPolicyMetadata" ....... 48
5.2.2.2. The Association Class
"SUPAHasPolicyMetadataDetail" .................. 48
5.3. The Abstract Class "SUPAPolicyStructure" ................. 48
5.3.1. SUPAPolicyStructure Attributes ...................... 49
5.3.1.1. The Attribute "supaPolContinuumLevel" .......... 49
5.3.1.2. The Attribute "supaPolDeployStatus" ............ 49
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5.3.2. SUPAPolicyStructure Relationships ................... 49
5.3.2.1. The Aggregation "SUPAHasPolicySource" .......... 49
5.3.2.2. The Association Class
"SUPAHasPolicySourceDetail" .................... 50
5.3.2.3. The Aggregation "SUPAIsTargetOf" ............... 50
5.3.2.4. The Association Class "SUPAIsTargetOfDetail" .. 50
5.4. The Abstract Class "SUPAPolicyStructureAtomic" ........... 50
5.4.1. SUPAPolicyStructureAtomic Attributes ................ 51
5.4.1.1. The Attribute "supaPolExecStatus" .............. 51
5.4.1.2. The Attribute "supaPolExecFailStrategy" ........ 51
5.4.1.3. The Attribute "supaPolExecFailTakeActionName" .. 52
5.4.1.4. The Attribute "supaPolExecFailTakeActionRes" .. 52
5.4.2. SUPAPolicyStructureAtomic Relationships ............. 52
5.4.2.1. The Aggregation "SUPAHasPolicyClause" .......... 53
5.4.2.2. The Association Class
"SUPAHasPolicyClauseDetail" .................... 53
5.5. The Concrete Class "SUPAPolicyStructureComposite" ........ 53
5.5.1. SUPAPolicyStructureComposite Attributes ............. 54
5.5.2. SUPAPolicyStructureComposite Relationships ........... 54
5.5.2.1. The Aggregation "SUPAHasPolicy" ................ 54
5.5.2.2. The Association Class "SUPAHasPolicyDetail" ..... 54
5.6. The Abstract Class "SUPAPolicyComponentStructure" ........ 54
5.6.1. SUPAPolicyComponentStructure Attributes ............. 55
5.6.1.1. The Attribute "supaAllowsExternalAccess" ....... 55
5.6.1.2. The Attribute "supaAllowsExternalUpdate" ....... 55
5.6.2. SUPAPolicyComponentStructure Relationships .......... 55
5.7. The Abstract Class "SUPAPolicyClause" .................... 55
5.7.1. SUPAPolicyClause Attributes ......................... 56
5.7.1.1. The Attribute "supaPolStmtAdminStatus" ......... 56
5.7.1.2. The Attribute "supaPolStmtExecStatus" .......... 56
5.7.2. SUPAPolicyClause Relationships ...................... 57
5.8. The Concrete Class "SUPAEncodedClause" ................... 57
5.8.1. SUPAEncodedClause Attributes ........................ 58
5.8.1.1. The Attribute "supaClauseContent" .............. 58
5.8.1.2. The Attribute "supaClauseFormat" ............... 58
5.8.1.3. The Attribute "supaClauseResponse" ............. 58
5.8.2. SUPAEncodedClause Relationships ..................... 58
5.9. The Abstract Class "SUPAPolicyComponentDecorator" ....... 59
5.9.1. The Decorator Pattern ............................... 59
5.9.2. SUPAPolicyComponentDecorator Attributes .............. 61
5.9.2.1. The Attribute "supaPolCompConstraintEncoding" .. 61
5.9.2.2. The Attribute "supaAPolCompConstraint[0..n]" ... 61
5.9.3. SUPAPolicyComponentDecorator Relationships .......... 61
5.9.3.1. The Aggregation
"SUPAHasDecoratedPolicyComponent" .............. 62
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5.9.3.2. The Association Class
"SUPAHasDecoratedPolicyComponentDetail" ........ 62
5.9.3.2.1. The Attribute
"supaDecoratedConstraintsEncoding" ........ 62
5.9.3.2.2. The Attribute
"supaDecoratedConstraints[1..n]" .......... 63
5.9.4. Illustration of Constraints in the Decorator Pattern 63
5.10. The Abstract Class "SUPAPolicyTerm" ..................... 64
5.10.1. SUPAPolicyTerm Attributes .......................... 65
5.10.1.1. The Attribute "supaPolTermIsNegated" .......... 65
5.10.2. SUPAPolicyTerm Relationships ....................... 65
5.11. The Concrete Class "SUPAPolicyVariable" ................. 65
5.11.1. Problems with the RFC3460 Version of PolicyVariable 66
5.11.1.1. Object Bloat .................................. 66
5.11.1.2. Object Explosion .............................. 67
5.11.1.3. Specification Ambiguities ..................... 67
5.11.2. SUPAPolicyVariable Attributes ...................... 68
5.11.2.1. The Attribute "supaPolVarContent" ............. 68
5.11.2.2. The Attribute "supaPolVarType" ................ 68
5.11.3. SUPAPolicyVariable Relationships ................... 69
5.12. The Concrete Class "SUPAPolicyOperator" ................. 69
5.12.1. Problems with the RFC3460 Version .................. 69
5.12.2. SUPAPolicyOperator Attributes ...................... 70
5.12.2.1. The Attribute "supaPolOpType" ................. 70
5.12.3. SUPAPolicyVariable Relationships ................... 70
5.13. The Concrete Class "SUPAPolicyValue" .................... 70
5.13.1. Problems with the RFC3460 Version of PolicyValue ... 71
5.13.1.1. Object Bloat .................................. 71
5.13.1.2. Object Explosion .............................. 71
5.13.1.3. Lack of Constraints ........................... 72
5.13.1.4. Tightly Bound to the CIM Schema ............... 72
5.13.1.5. Specification Ambiguity ....................... 72
5.13.1.6. Lack of Symmetry .............................. 72
5.13.2. SUPAPolicyValue Attributes .......................... 72
5.13.2.1. The Attribute "supaPolValContent[0..n]" ....... 72
5.13.2.2. The Attribute "supaPolValType" ................ 73
5.13.3. SUPAPolicyVariable Relationships ................... 73
5.14. The Concrete Class "SUPAVendorDecoratedComponent" ....... 73
5.14.1. SUPAVendorDecoratedComponent Attributes ............ 73
5.14.1.1. The Attribute
"supaVendorDecoratedCompContent[0..n]" ......... 74
5.14.1.2. The Attribute "supaVendorDecoratedCompFormat" .. 74
5.14.2. SUPAVendorDecoratedComponent Relationships ......... 74
5.15. The Concrete Class "SUPAPolicyCollection" ............... 74
5.15.1. Motivation ......................................... 75
5.15.2. Solution ........................................... 75
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5.15.3. SUPAPolicyCollection Attributes .................... 75
5.15.3.1. The Attribute "supaPolCollectionContent[0..n]" 76
5.15.3.2. The Attribute "supaPolCollectionDataType" ..... 76
5.15.3.3. The Attribute "supaPolCollectionFunction" ..... 76
5.15.3.4. The Attribute "supaPolCollectionIsOrdered" .... 76
5.15.3.5. The Attribute "supaPolCollectionType" ......... 76
5.15.4. SUPAPolicyCollection Relationships ................. 77
5.16. The Concrete Class "SUPAPolicySource" ................... 77
5.16.1. SUPAPolicySource Attributes ........................ 78
5.16.2. SUPAPolicySource Relationships ..................... 78
5.16.2.1. The Association Class
"SUPAHasPolicySourceDetail" ................... 78
5.16.2.1.1. The Attribute "SUPAPolSrcIsAuthenticated" 78
5.16.2.1.2. The Attribute "supaPolicySrcIsTrusted" ... 78
5.17. The Concrete Class "SUPAPolicyTarget" ................... 79
5.17.1. SUPAPolicyTarget Attributes ........................ 79
5.17.2. SUPAPolicyTarget Relationships ..................... 79
5.17.2.1. The Aggregation "SUPAHasPolicyTarget" ......... 79
5.17.2.2. The Association Class
"SUPAHasPolicyTargetDetail" ................... 80
5.17.2.2.1. The Attribute "SUPAPolTgtIsAuthenticated" 80
5.17.2.2.2. The Attribute "supaPolTgtIsEnabled" ...... 80
5.18. The Abstract Class "SUPAPolicyMetadata" ................. 80
5.18.1. SUPAPolicyMetadata Attributes ...................... 81
5.18.1.1. The Attribute "supaPolMetadataDescription" .... 81
5.18.1.2. The Attribute "supaPolMetadataIDContent" ...... 81
5.18.1.3. The Attribute "supaPolMetadataIDFormat" ....... 81
5.18.1.4. The Attribute "supaPolicyName" ................ 82
5.18.2. SUPAPolicyMetadata Relationships ................... 82
5.18.3. The Abstract Class "SUPAHasPolicyMetadataDetail" ... 82
5.18.3.1. The Attribute "supaPolMetadataIsApplicable" ... 82
5.18.3.2. The Attribute
"supaPolMetadataConstraintEncoding" ........... 83
5.18.3.3. The Attribute
"supaPolMetadataPolicyConstraints[0..n]" ...... 83
6. SUPA ECAPolicyRule Information Model ........................... 84
6.1. Overview ................................................. 84
6.2. Constructing a SUPAECAPolicyRule ......................... 85
6.3. Working With SUPAECAPolicyRules .......................... 86
6.4. The Concrete Class "SUPAECAPolicyRule" ................... 88
6.4.1. SUPAECAPolicyRule Attributes ........................ 89
6.4.1.1. The Attribute "supaECAPolicyIsMandatory" ....... 90
6.4.1.2. The Attribute "supaECAPolicyPriority" .......... 90
6.4.1.3. The Attribute "supaECAPolicyRuleStatus" ........ 90
6.4.2. SUPAECAPolicyRule Relationships ..................... 90
6.5. The Concrete Class "SUPAECAPolicyRuleAtomic" ............. 90
6.5.1. SUPAECAPolicyRuleAtomic Attributes .................. 90
6.5.2. SUPAECAPolicyRuleAtomic Relationships ............... 90
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6.6. The Concrete Class "SUPAECAPolicyRuleComposite" .......... 91
6.6.1. SUPAECAPolicyRuleComposite Attributes ............... 91
6.6.1.1. The Attribute "supaECAEvalStrategy" ............ 91
6.6.2. SUPAECAPolicyRuleComposite Relationships ............ 92
6.6.2.1. The Aggregation "SUPAHasECAPolicyRule" ......... 92
6.6.3. The Association Class "SUPHasECAPolicyRuleDetail" ... 92
6.6.3.1. The Attribute "supaECAPolicyIsDefault" ......... 92
6.7. The Abstract Class "SUPABooleanClause" ................... 92
6.7.1. SUPABooleanClause Attributes ........................ 93
6.7.1.1. The Attribute "supaBoolIsCNF" .................. 93
6.7.1.2. The Attribute "supaBoolIsNegated" .............. 94
6.7.2. SUPABooleanClause Relationships ..................... 94
6.8. The Concrete Class "SUPABooleanClauseAtomic" ............. 94
6.8.1. SUPABooleanClauseAtomic Attributes .................. 94
6.8.2. SUPABooleanClauseAtomic Relationships ............... 94
6.9. The Concrete Class "SUPABooleanClauseComposite" .......... 94
6.9.1. SUPABooleanClauseComposite Attributes ............... 94
6.9.1.1. The Attribute "supaPolStmtBindValue" .................... 95
6.9.2. SUPABooleanClauseComposite Relationships ............ 95
6.9.2.1. The Aggregation "SUPAHasBooleanClause" ......... 95
6.9.3. The Concrete Class "SUPAHasBooleanClauseDetail" ..... 95
6.9.3.1. SUPAHasBooleanClauseDetail Attributes .......... 95
6.10. The Abstract Class "SUPAECAComponent" ................... 96
6.10.1. SUPAECAComponent Attributes ........................ 96
6.10.2. SUPAECAComponent Relationships ..................... 96
6.11. The Concrete Class "SUPAPolicyEvent" .................... 96
6.11.1. SUPAPolicyEvent Attributes ......................... 96
6.11.1.1. The Attribute "supaPolicyEventIsPreProcessed" . 96
6.11.1.2. The Attribute "supaPolicyEventIsSynthetic" .... 96
6.11.1.3. The Attribute "supaPolicyEventTopic[0..n]" .... 96
6.11.1.4. The Attribute "supaPolicyEventDataType" ....... 97
6.11.1.5. The Attribute "supaPolicyEventData[1..n]" ..... 97
6.11.2. SUPAPolicyEvent Relationships ...................... 98
6.12. The Concrete Class "SUPAPolicyCondition" ................ 98
6.12.1. SUPAPolicyCondition Attributes ..................... 98
6.12.1.1. The Attribute "supaPolicyConditionDataType" ... 98
6.12.1.2. The Attribute "supaPolicyConditionData" ....... 98
6.12.2. SUPAPolicyEvent Relationships ...................... 98
6.13. The Concrete Class "SUPAPolicyAction" ................... 99
6.13.1. SUPAPolicyAction Attributes ........................ 99
6.13.1.1. The Attribute "supaPolicyActionDataType" ...... 99
6.13.1.2. The Attribute "supaPolicyActionData" .......... 99
6.13.1.3. The Attribute "supaPolicyActionResponse" ..... 100
6.13.2. SUPAPolicyAction Relationships .................... 100
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7. Examples ................................................... 100
8. Security Considerations ................................... 100
9. IANA Considerations ........................................ 100
10. Acknowledgments ........................................... 100
11. References ................................................ 100
11.1. Normative References ................................. 100
11.2. Informative References .............................. 101
Authors' Addresses ............................................ 102
Appendix A. Mathematical Logic Terminology and Symbology ..... 102
Appendix B. SUPA Logic Statement Information Model ........... 102
Appendix C. Brief Analyses of Previous Policy Work ........... 102
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1. Overview
This document defines an information model for representing
policies using a common extensible framework that is independent
of language, protocol, repository, and the level of abstraction of
the content and meaning of a policy. This enables a common set of
concepts defined in this information model to be mapped into
different representations of policy (e.g., procedural, imperative,
and declarative). It also enables different data models that use
different languages, protocols, and repositories to optimize
their usage. The definition of common policy concepts also
provides better interoperability by ensuring that each data
model can share a set of common concepts, independent of its
level of detail or the language, protocol, and/or repository
that it is using. It is also independent of the target data
model that will be generated.
This version of the information model focuses on defining one
type of policy rule: the event-condition-action (ECA) policy rule.
Accordingly, this document defines two sets of model elements:
1. A framework for defining the concept of policy,
independent of how policy is represented or used; this is
called the SUPA Generic Policy Information Model (GPIM)
2. A framework for defining a policy model that uses the
event-condition-action paradigm; this is called the SUPA
Eca Policy Rule Information Model (EPRIM), and extends
concepts from the GPIM.
The combination of the GPIM and the EPRIM provides an extensible
framework for defining policy that uses an event-condition-action
representation that is independent of data repository, data
definition language, query language, implementation language, and
protocol.
The Appendices describe how the structure of the GPIM defines a
set of generic concepts that enables other types of policies, such
as declarative (or "intent-based") policies, to be added later.
1.1. Introduction
Simplified Use of Policy Abstractions (SUPA) defines an interface
to a network management function that takes high-level, possibly
network-wide policies as input and creates element configuration
snippets as output. SUPA addresses the needs of operators and
application developers to represent multiple types of policy
rules, which vary in the level of abstraction, to suit the needs
of different actors [1], [10].
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Different constituencies of users would like to use languages that
use terminology and concepts that are familiar to each constituency.
Rather than require multiple software systems to be used for each
language, a common information model enables these different
languages to be mapped to terms in the information model. This
facilitiates the use of a single software system to generate data
models for each language. In the example shown in Figure 1 (which
is a simplified policy continuum [10]), each constituency needs
different grammars using different concepts and terminologies to
match their skill set. This is shown in Figure 1. A unified
information model is one way to build a consensual lexicon that
enables terms from one language to be mapped to terms of another
language.
+---------------------+
+---------------+ \| High-level Policies | \+-------------+
| Business User |----| Without Technical |----| Language #1 |
+---------------+ /| Terminology | /+-------------+
+---------------------+
+---------------------+
+---------------+ \| Policies That Use | \+-------------+
| Developer |----| Classes, Attributes,|----| Language #2 |
+---------------+ /| Relationships, ... | /+-------------+
+---------------------+
... ... ...
+---------------------+
+---------------+ \| Low-level Policies | \+-------------+
| Admin |----| with Technology- |----| Language #n |
+---------------+ /| Specific Terms in a | /+-------------+
| Specific Language |
+---------------------+
Figure 1. Different Constituencies Need Different Policies
More importantly, an information model defines concepts in a
uniform way, enabling formal mapping processes to be developed to
translate the information model to a set of data models. This
simplifies the process of constructing software to automate the
policy management process. It also simplifies the language
generation process, though that is beyond the scope of this
document.
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This common framework takes the form of an information model that
is divided into one high-level module and any number of lower-
level modules, where each lower-level module extends the concepts
of the single high-level module. Conceptually, a set of model
elements (e.g., classes, attributes, and relationships) are used
to define the Generic Policy Information Model (GPIM); this module
defines a common set of policy management concepts that are
independent of the type of policy (e.g., imperative, procedural,
declarative, or otherwise). Then, any number of additional modules
are derived from the GPIM; each additional module MUST extend the
GPIM to define a new type of policy rule by adding to the GPIM.
(Note: using extensions preserves the core interoperability, as
compared with modification of the base GPIM, which would adversely
compromise interoperability.
The SUPA Eca Policy Rule Information Model (EPRIM) extends the
GPIM to represent policy rules that use the Event-Condition-Action
(ECA) paradigm. (The Appendices describe the SUPA Logic Statement
Information Model (LSIM), which shows how to extend the GPIM to
represent statements that are subsets of either Propositional
Logic (PL) or First-Order Logic (FOL), respectively. Both of these
logics are types of declarative logic. Note that the LSIM is
currently out of scope. However, it is outlined as a set of
Appendices in this document to get feedback on its utility.
1.2. Changes Since Version -02
There are several main changes in this version of this document
compared to the previous version (-02) of this document. They are:
1) The GPIM has been redesigned to be more compact, making it
easier to construct data models
2) As part of 1), additional options for constructing data
models have been added to the GPIM
3) The LSIM has been moved into an Appendix, since the latest
charter makes it currently out of scope. However, it is
important to ensure that the GPIM can serve as a single
foundation that different types of policies can all be
derived from to ensure that SUPA can interact with other
SDOs, as well as for future work in the IETF.
4) Examples and figures have been added to clarify the model
2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in [RFC2119]. In
this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to
be interpreted as carrying [RFC2119] significance.
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3. Terminology
This section defines acronyms, terms, and symbology used in the
rest of this document.
3.1. Acronyms
CLI Command Line Interface
CRUD Create, Read, Update, Delete
CNF Conjunctive Normal Form
DNF Disjunctive Normal Form
ECA Event-Condition-Action
EPRIM (SUPA) ECA Policy Rule Information Model
GPIM (SUPA) Generic Policy Information Model
NETCONF Network Configuration protocol
OAM&P Operations, Administration, Management, and Provisioning
OID Object IDentifier
PAP Policy Administration Point
PDP Policy Decision Point
PEP Policy Enforcement Point
PIP Policy Information Point
PR Policy Repository
PXP Policy Execution Point
SUPA Simplified Use of Policy Abstractions
TMF TeleManagent Forum (TM Forum)
UML Unified Modeling Language
URI Uniform Resource Identifier
YANG A data definition language for use with NETCONF
ZOOM Zero-touch Orchestration, Operations, and Management
(a TMF project that also works on information models)
3.2. Definitions
This section defines the terminology that is used in this document.
3.2.1. Core Terminology
The following subsections define the terms "information model" and
"data model", as well as "container" and "policy container".
3.2.1.1. Information Model
An information model is a representation of concepts of interest
to an environment in a form that is independent of data repository,
data definition language, query language, implementation language,
and protocol.
Note: this definition is more specific than that of [RFC3198], so
as to focus on the properties of information models.
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3.2.1.2. Data Model
A data model is a representation of concepts of interest to an
environment in a form that is dependent on data repository, data
definition language, query language, implementation language, and
protocol (typically, but not necessarily, all three).
Note: this definition is more specific than that of [RFC3198], so
as to focus on the properties of data models that are generated
from information models.
3.2.1.3. Abstract Class
An abstract class is a class that cannot be directly instantiated.
It MAY have abstract or concrete subclasses. It is denoted with a
capital A near the top-left side of the class.
3.2.1.4. Concrete Class
A concrete class is a class that can be directly instantiated. Note
that classes are either abstract or concrete. In addition, once a
class has been defined as concrete in the hierarchy, all of its
subclasses MUST also be concrete. It is denoted with a capital C
near the top-left side of the class.
3.2.1.5. Container
A container is an object whose instances may contain zero or more
additional objects, including container objects. A container
provides storage, query, and retrieval of its contained objects
in a well-known, organized way.
3.2.1.6. PolicyContainer
In this document, a PolicyContainer is a special type of container
that provides at least the following three functions:
1. It uses metadata to define how its content is interpreted
2. It separates the content of the policy from the
representation of the policy
3. It provides a convenient control point for OAMP operations
The combination of these three functions enables a PolicyContainer
to define the behavior of how its constituent components will be
accessed, queried, stored, retrieved, and how they operate.
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3.2.2. Policy Terminology
The following terms define different policy concepts used in the
SUPA Generic Policy Information Model (GPIM). Note that the
prefix "SUPA" is used for all classes and relationships defined
in this model to ensure name uniqueness. Similarly, the prefix
"supa" is defined for all SUPA class attributes.
3.2.2.1. SUPAPolicyObject
A SupaPolicyObject is the root of the GPIM class hierarchy. It is
an abstract class that all classes inherit from, except the
SUPAPolicyMetadata class.
3.2.2.2. SUPAPolicy
A SUPAPolicy is, in this version of this document, an ECA policy
rule that is a type of PolicyContainer. The PolicyContainer MUST
contain an ECA policy rule, SHOULD contain one or more
SUPAPolicyMetadata objects, and MAY contain other elements that
define the semantics of the policy rule. Policies are generically
defined as a means to monitor and control the changing and/or
maintaining of the state of one or more managed objects [1]. In
this context, "manage" means that at least create, read, query,
update, and delete functions are supported.
3.2.2.3. SUPAPolicyClause
A SUPAPolicyClause is an abstract class. Its subclasses define
different types of clauses that are used to create the content
for different types of SUPAPolicies.
For example, the SUPAPolicyBooleanClause subclass models the
content of a SUPAPolicy as a Boolean clause, where each Boolean
clause is made up of a set of reusable objects. In contrast, a
SUPAPololicyEncodedClause encodes the entire clause as a set of
attributes. All types of SUPAPolicies MUST use one or more
SUPAPolicyClauses to construct a SUPAPolicy.
3.2.2.4. SUPAECAPolicyRule
An Event-Condition-Action (ECA) Policy (SUPAECAPolicyRule) is an
abstract class that is a type of PolicyContainer. It represents
a policy rule as a three-tuple, consisting of an event, a
condition, and an action clause. In an information model, this
takes the form of three different aggregations, one for each
clause. Each clause MUST be represented by at least one
SUPAPolicyClause. Optionally, the SUPAECAPolicyRule MAY contain
zero or more SUPAPolicySources, zero or more SUPAPolicyTargets,
and zero or more SUPAPolicyMetadata objects.
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3.2.2.5. SUPAMetadata
Metadata is, literally, data about data. SUPAMetadata is an
abstract class that contains prescriptive and/or descriptive
information about the object(s) to which it is attached. While
metadata can be attached to any information model element, this
document only considers metadata attached to classes and
relationships.
When defined in an information model, each instance of the
SUPAMetadata class MUST have its own aggregation relationship
with the set of objects that it applies to. However, a data model
MAY map these definitions to a more efficient form (e.g.,
flattening the object instances into a single object instance).
3.2.2.6. SUPAPolicyTarget
SUPAPolicyTarget is an abstract class that defines a set of
managed objects that may be affected by the actions of a
SUPAPolicyClause. A SUPAPolicyTarget may use one or more
mechanisms to identify the set of managed objects that it
affects; examples include OIDs and URIs.
When defined in an information model, each instance of the
SUPAPolicyTarget class MUST have its own aggregation
relationship with each SUPAPolicy that uses it. However, a
data model MAY map these definitions to a more efficient form
(e.g., flattening the SUPAPolicyTarget, SUPAMetadata, and
SUPAPolicy object instances into a single object instance).
3.2.2.7. SUPAPolicySource
SUPAPolicySource is an abstract class that defines a set of
managed objects that authored this SUPAPolicyClause. This is
required for auditability. A SUPAPolicySource may use one or more
mechanisms to identify the set of managed objects that authored it;
examples include OIDs and URIs. Specifically, policy CRUD MUST be
subject to authentication and authorization, and MUST be auditable.
Note that the mechanisms for doing these three operations are
currently not included, and are for further discussion.
When defined in an information model, each instance of the
SUPAPolicySource class MUST have its own aggregation relationship
with each SUPAPolicy that uses it. However, a data model MAY map
these definitions to a more efficient form (e.g., flattening the
SUPAPolicySource, SUPAMetadata, and SUPAPolicy object instances
into a single object instance).
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3.2.3. Modeling Terminology
The following terms define different types of relationships used
in the information models of the SUPA Generic Policy Information
Model (GPIM).
3.2.3.1. Inheritance
Inheritance makes an entity at a lower level of abstraction (e.g.,
the subclass) a type of an entity at a higher level of abstraction
(e.g., the superclass). Any attributes and relationships that are
defined for the superclass are also defined for the subclass.
However, a subclass does NOT change the characteristics or behavior
of the attributes or relationships of the superclass that it
inherits from. Formally, this is called the Liskov Substitution
Principle [7]. This principle is one of the key characteristics
that is NOT followed in [4], [6], [RFC3060], and [RFC3460].
A subclass MAY add new attributes and relationships that refine
the characteristics and/or behavior of it compared to its
superclass. A subclass MUST NOT change inherited attributes or
relationships.
3.2.3.2. Relationship
A relationship is a generic term that represents how a first set
of entities interact with a second set of entities. A recursive
relationship sets the first and second entity to the same entity.
There are three basic types of relationships, as defined in the
subsections below: associations, aggregations, and compositions.
A subclass MUST NOT change the multiplicity (see section 3.2.3.7)
of a relationship that it inherits. A subclass MUST NOT change any
attributes of a relation that it inherits that is realized using
an association class (see section 3.2.3.6).
3.2.3.3. Association
An association represents a generic dependency between a first
and a second set of entities. In an information model, an
association MAY be represented as a class.
3.2.3.4. Aggregation
An aggregation is a stronger type (i.e., more restricted
semantically) of association, and represents a whole-part
dependency between a first and a second set of entities. Three
objects are defined by an aggregation: the first entity, the
second entity, and a new third entity that represents the
combination of the first and second entities.
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The entity owning the aggregation is referred to as the
"aggregate", and the entity that is aggregated is referred to as
the "part". In an information model, an aggregation MAY be
represented as a class.
3.2.3.5. Composition
A composition is a stronger type (i.e., more restricted
semantically) of aggregation, and represents a whole-part
dependency with two important behaviors. First, an instance of the
part is included in at most one instance of the aggregate at a
time. Second, any action performed on the composite entity (i.e.,
the aggregate) is propagated to its constituent part objects.
For example, if the composite entity is deleted, then all of its
constituent part entities are also deleted. This is not true of
aggregations or associations - in both, only the entity being
deleted is actually removed, and the other entities are unaffected.
In an information model, a composition MAY be represented as
a class.
3.2.3.6. Association Class
A relationship may be implemented as an association class. This is
used to define the relationship as having its own set of features.
More specifically, if the relationship is implemented as an
association class, then the attributes of the association class, as
well as other relationships that the association class participates
in, may be used to define the semantics of the relationship. If the
relationship is not implemented as an association class, then no
additional semantics (beyond those defined by the type of the
relationship) are expressed by the relationship.
3.2.3.7. Multiplicity
A specification of the range of allowable cardinalities that a set
of entities may assume. This is always a pair of ranges, such as
1 - 1 or 0..n - 2..5.
3.2.3.8. Navigability
A relationship may have a restriction on the ability of an object
at one end of the relationship to access the object at the other
end of the relationship. This document defines two choices:
1. Each object is navigable by the other, which is indicated
by NOT providing any additional symbology, or
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2. An object A can navigate to object B, but object B cannot
navigate to object A. This is indicated by an open-headed
arrow pointing to the object that cannot navigate to the
other object. In this example, the arrow would be pointing
at object B.
Examples of navigability are:
+---------+ 3..4 +---------+
| | 1..2 \| |
| Class A |--------------| Class B |
| | /| |
+---------+ +---------+
This is an association. Class A can navigate to Class B, but Class
B cannot navigate to Class A. This is a mandatory association,
since none of the multiplicities contain a '0'. This association
reads as follows:
Class A depends on 3 to 4 instances of Class B, and
Class B depends on 1 to 2 instances of Class A.
3.3. Symbology
The following symbology is used in this document:
3.3.1. Inheritance
Inheritance: a subclass inherits the attributes and relationships
of its superclass, as shown below:
+------------+
| Superclass |
+------+-----+
/ \
I
I
I
+------+-----+
| Subclass |
+------------+
3.3.2. Association
Association: Class B depends on Class A, as shown below:
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+---------+ +---------+
+---------+ +---------+ | | \| |
| Class A |------| Class B | | Class A |------| Class B |
+---------+ +---------+ | | /| |
+---------+ +---------+
association with no association with
navigability restrictions navigability restrictions
3.3.3. Aggregation
Aggregation: Class B is the part, Class A is the aggregate,
as shown below:
+---------+ +---------+ +---------+
| |/ \ +---------+ | |/ \ \| |
| Class A | A ---| Class B | | Class A | A ------| Class B |
| |\ / +---------+ | |\ / /| |
+---------+ +---------+ +---------+
aggregation with no aggregation with
navigability restrictions navigability restrictions
3.3.4. Composition
Composition: Class B is the part, Class A is the composite,
as shown below:
+---------+ +---------+ +---------+
| |/ \ +---------+ | |/ \ \| |
| Class A | C ---| Class B | | Class A | C ------| Class B |
| |\ / +---------+ | |\ / /| |
+---------+ +---------+ +---------+
composition with no composition with
navigability restrictions navigability restrictions
3.3.5. Association Class
Association Class: Class C is the association class implementing
the relationship D between classes A and B
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+---------+ +---------+
| Class A |----+-----| Class B |
+---------+ ^ +---------+
|
|
+----------+----------+
| Association Class C |
+---------------------+
3.3.6. Abstract vs. Concrete Classes
In UML, abstract classes are denoted with their name in italics.
For this draft, a capital 'A' will be placed at either the top
left or right corner of the class to signify that the class is
abstract. Similarly, a captial 'C' will be placed in the same
location to represent a concrete class. This is shown below.
A C
+---------+ +---------+
| Class A | | Class B |
+---------+ +---------+
An Abstract Class A Concrete Class
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4. Policy Abstraction Architecture
This section describes the motivation for the policy abstractions
that are used in SUPA. The following abstractions are provided:
o The GPIM defines a technology-neutral information model that
can express the concept of Policy.
o All classes, except for SUPAPolicyMetadata, inherit from
SUPAPolicyObject, or one of its subclasses
o SUPAPolicyObject and SUPAPolicyMetadata are designed to
inherit from classes in another model; the GPIM does not
define an "all-encompassing" model.
o This version of this document restricts the expression of
Policy to a set of event-condition-action statements.
o However, the purpose of the GPIM is to enable different
policies that have fundamentally different representations
to share common model elements. This abstraction of the
content of a Policy from its representation is supported by:
o All policy rules (of which SUPAECAPolicyRule is the
first example of a concrete class) are derived from
the SUPAPolicyStructure class.
o All objects that are components of policy rules are
derived from the SUPAPolicyComponentxxx`Structure class.
o A SUPAPolicy MUST contain at least one SUPAPolicyClause.
o A SUPAPolicy MAY specify one or more SUPAPolicyTarget,
SUPAPolicySource, and SUPAPolicyMetadata objects to
augment the semantics of the SUPAPolicy
o A SUPAPolicyClause has two subclasses:
o A SUPAPolicyBooleanClause, which is used to build
SUPAECAPolicyRules from reusable objects.
o A SUPAPolicyEncodedClause, which is used for using
attributes instead of objects to construct a
SUPAECAPolicyRule.
o A SUPAECAPolicyRule defines the set of events and conditions
that are responsible for executing its actions; it MUST have
at least one event clause, at least one condition clause, and
at least one action clause.
o SUPAMetadata MAY be defined for any SUPAPolicyObject class.
o SUPAMetadata MAY be prescriptive and/or descriptive in nature.
Please see the Appendices for experimental definitions of
declarative policies. Note that they also are derived from the
GPIM, and extend (but do not change) the above abstractions.
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4.1. Motivation
The power of policy management is its applicability to many
different types of systems. There are many different actors that
can use a policy management system, including end-users, operators,
application developers, and administrators. Each of these
constituencies have different concepts and skills, and use
different terminology. For example, an operator may want to express
an operational rule that states that only Platinum and Gold users
can use streaming multimedia applications. As a second example, a
network administrator may want to define a more concrete policy
rule that looks at the number of dropped packets and, if that
number exceeds a programmable threshold, changes the queuing and
dropping algorithms used.
SUPA may be used to define other types of policies, such as for
systems and operations management; an example is: "All routers and
switches must have password login disabled". See section 3 of [8]
for additional declarative and ECA policy examples.
All of the above examples are commonly referred to as "policy
rules", but they take very different forms, since they are at very
different levels of abstraction and typically authored by
different actors. The first was very abstract, and did not contain
any technology-specific terms, while the second was more concrete,
and likely used technical terms of a general (e.g., IP address
range, port numbers) as well as a vendor-specific nature (e.g.,
specific queuing, dropping, and/or scheduling algorithms
implemented in a particular device). The third restricted the type
of login that was permissible for certain types of devices in the
environment.
Note that the first two policy rules could directly affect each
other. For example, Gold and Platinum users might need different
device configurations to give the proper QoS markings to their
streaming multimedia traffic. This is very difficult to do if a
common policy model does not exist, especially if the two policies
are authored by different actors that use different terminology
and have different skill sets. More importantly, the users of
these two policies likely have different job responsibilities.
They may have no idea of the concepts used in each policy. Yet,
their policies need to interact in order for the business to
provide the desired service. This again underscores the need for
a common policy framework.
Certain types of policy rules (e.g., ECA) may express actions, or
other types of operations, that contradict each other. SUPA
provides a rich object model that can be used to support language
definitions that can find and resolve such problems.
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4.2. SUPA Approach
The purpose of the SUPA Generic Policy Information Model (GPIM) is
to define a common framework for expressing policies at different
levels of abstraction. SUPA uses the GPIM as a common vocabulary
for representing policy concepts that are independent of language,
protocol, repository, and level of abstraction. This enables
different actors to author and use policies at different levels of
abstraction. This forms a policy continuum [1] [2], where more
abstract policies can be translated into more concrete policies,
and vice-versa.
Most systems define the notion of a policy as a single entity.
This assumes that all users of policy have the same terminology,
and use policy at the same level of abstraction. This is rarely,
if ever, true in modern systems. The policy continuum defines a
set of views (much like RM-ODP's viewpoints [9]) that are each
optimized for a user playing a specific role. SUPA defines the
GPIM as a standard vocabulary and set of concepts that enable
different actors to use different formulations of policy. This
corresponds to the different levels in the policy continuum, and
as such, can make use of previous experience in this area.
It may be necessary to translate a Policy from a general to a more
specific form (while keeping the abstraction level the same). For
example, the declarative policy "Every network attached to a VM
must be a private network owned by someone in the same group as
the owner of the VM" may be translated to more formal form (e.g.,
Datalog (as in OpenStack Congress). It may also be necessary to
translate a Policy to a different level of abstraction. For
example, the previous Policy may need to be translated to a form
that network devices can process directly. This requires a common
framework for expressing policies that is independent of the level
of abstraction that a Policy uses.
4.3. SUPA Generic Policy Information Model Overview
Figure 2 illustrates the approach for representing policy rules
in SUPA. The top two layers are defined in this document; the
bottom layer (Data Models) are defined in separate documents.
Conceptually, the GPIM defines a set of objects that define the
key elements of a Policy independent of how it is represented or
its content. As will be shown, there is a significant difference
between SUPAECAPolicyRules (see Section 6) and other types of
policies (see Section 7). In principle, other types of SUPAPolicies
could be defined, but the current charter is restricted to using
only event-condition-action SUPAPolicies as exemplars.
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+----------------------------------------------+
| SUPA Generic Policy Information Model (GPIM) |
+----------------------+-----------------------+
/ \
|
|
+-----------------+--------------+
| |
| |
+-----------+---------------+ +-------------+-------------+
| SUPAECAPolicyRule | | Other Policy Models that |
| Information Model (EPRIM) | | are Derived from the GPIM |
+-----------+---------------+ +-------------+-------------+
/ \ / \
| |
| |
+-----------+-----------+ +-----------+------------+
| ECAPolicyRule | | Other Types of |
| Data Model | | Data Models |
+-----------------------+ +------------------------+
Figure 2. Overview of SUPA Policy Rule Abstractions
This draft defines the GPIM and EPRIM. Note that there is only
ONE GPIM and ONE EPRIM. While both can be extended, it is
important to limit the number of information models to one, in
order to avoid defining conflicting concepts at this high a
level of abstraction. Similarly, if the GPIM and EPRIM are part
of another information model, then they should collectively
still define a single information model. The GPIM defines the
following concepts:
o A class defining the top of the GPIM class hierarchy, called
SUPAPolicyObject
o Four subclasses of SUPAPolicyObject, representing:
o the top of the PolicyRule hierarchy, called
SUPAPolicyStructure
o the top of the PolicyRule component hierarchy, called
SUPAPolicyComponentStructure
o PolicySource
o PolicyTarget
The SUPAPolicyStructure hierarchy has two main subclasses, an
atomic (stand-alone) and composite (hierarchy of) PolicyRule.
The SUPAPolicyComponentStructure hierarchy has two main
subclasses:
o A SUPAPolicyClause (the building block of all Policies)
o A SUPAPolicyComponentDecorator, which uses the decorator
pattern to define objects that make up the content of
the SUPAPolicyClause
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This yields the following high-level structure:
A
+------------------+
| SUPAPolicyObject |
+--------+---------+
I
I
+------------+------------------+
I I
A I A I
+--------+------------+ +------------+-----------------+
| SUPAPolicyStructure | | SUPAPolicyComponentStructure |
+--------+------------+ +------------+-----------------+
I I
I I
+-------+ +-------+-------+
I I I I
A I I A I I
+-------------+----+ I +-----------+---------+ I
| SUPAPolicyAtomic | I | SUPAPolicyClause | I
+------------------+ I +---------------------+ I
C I A I
+-----------------+---+ +--------------------+---------+
| SUPAPolicyComposite | | SUPAPolicyComponentDecorator |
+---------------------+ +------------------------------+
Figure 3. Functional View of the Top-Level GPIM
Note that all classes except the SUPAPolicyComposite class are
defined as abstract. This provides more freedom for the data
modeler in implementing the data model. For example, if the data
model uses an object-oriented language, such as Java, then the
above structure enables all of the abstract classes to be
collapsed to a single concrete class. If this is done, attributes
as well as relationships are inherited.
4.3.1. SUPAPolicyObject
A SUPAPolicyObject serves as a single root of the SUPA system
(i.e., all other classes in the model are subclasses of the
SUPAPolicyObject class). This simplifes code generation and
reusability.
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4.3.2. SUPAPolicyStructure
SUPAPolicyStructure is an abstract superclass that serves as the
base class for defining all types of policies (though in this
version of this document, this is limited to ECA policies). It
serves as a convenient aggregation point to define atomic and
composite SUPAPolicies; it also enables PolicySources and/or
PolicyTargets to be associated with a given set of Policies.
SUPA Policies are defined as either a stand-alone PolicyContainer
(i.e., a subclass of SUPAPolicyAtomic), or a hierarchy of
PolicyContainers (i.e., as an instance of or subclass of
SUPAPolicyComposite). A PolicyContainer specifies the
structure, content, and optionally, source, target, and metadata
information for the Policy.
This document defines a SUPAPolicy as an ECA Policy Rule, though
the GPIM enables other types of policies to be defined and used
with an ECA policy rule. The GPIM model is used in [2] and [5],
along with extensions that allow [2] and [5] to define multiple
types of policies that are derived from the GPIM. They also allow
different combinations of different types of policy rules to be
used with each other. However, the ability to define different
types of policy rules, let alone combine different types of
policies, is NOT true of [RFC3060], [RFC3460], [4] and [6];
[RFC3060], [RFC3460], and [4] are limited to only defining
condition-action rules, and [6] is limited to only defining ECA
policy rules.
4.3.3. SUPAPolicyComponentStructure
SUPAPolicyComponentStructure is an abstract superclass that serves
as the base class for defining the set of policy components that
are used to make up a given Policy. From an information model
point-of-view, this isolates the various subclasses of
SUPAPolicyComponentStructure, and controls how they are used by
other different elements of the SUPAPolicy hierarchy.
4.3.4. SUPAPolicyClause
All policies derived from the GPIM are made up of one or more
SUPAPolicyClauses, which define the content of the Policy.
This enables a Policy of one type (e.g., ECA) to invoke Policies
of the same or different types. This is an abstract class, and
serves as a convenient aggregation point for assembling other
objects that make up a SUPAPolicyClause.
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The GPIM defines a single concrete subclass of SUPAPolicyClause.
called SUPAEncodedClause. This is a generic clause, and can be
used by any type of Policy in a stand-alone fashion or to
construct more complex clauses that form a policy statement. Note
that there is no need to create the SimplePolicyCondition and
ComplexPolicyCondition objects defined in [RFC3460].
Other models define additional subclasses of SUPAPolicyStatment
(e.g., the EPRIM defines a SUPABooleanClause, which is specific to
an ECA Policy Rule, and the LSIM (see Appendix) defines a
SUPALogicClause, which is specific to declarative policies). This
structure enables different types of Policies, which have
different forms of content and structure, to all be represented
as subclasses of SUPAPolicyClause. This enables the designer
to use multiple types of Policies.
A SUPAPolicyClause is defined as an object. Therefore, clauses and
sets of clauses are objects, which promotes reusability.
4.3.5. SUPAPolicyComponentDecorator
One of the problems in building a policy model is the tendency to
have a multitude of classes, and hence object instances, to
represent different combinations of policy events, conditions, and
actions. This can lead to class and or relationship explosion, as
if the case in [RFC3460], [4], and [6].
SUPAPolicyClauses are constructed using the Decorator Pattern
[11]. This is a design pattern that enables behavior to be
selectively added to an individual object, either statically or
dynamically, without affecting the behavior of other objects from
the same class. The decorator pattern uses composition, instead of
inheritance, to avoid class and relationship explosion. The
decorator pattern also enable new objects to be composed from
parts or all of existing objects without affecting the existing
objects.
This enables the resulting SUPAPolicyClause to be constructed
completely from objects in the SUPA information model. This
facilitates the construction of policies at runtime by a machine.
This is also true of [2] and [5]; however, this is NOT true of
[RFC3060], [RFC3460], [4] and [6], since they lack both the
abstraction of a common SUPAPolicyClause and do not use the
decorator (or similar) design pattern.
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SUPAPolicyComponentDecorator defines four types of objects that
can be used to form a SUPAPolicyClause. Each object may be used
with all other objects, if desired. The first three are defined
in the GPIM, with the last defined in the EPRIM. The objects are:
o SUPAPolicyTerm, which enables a clause to be defined in a
canonical {variable, operator, value} form
o SUPAVendorDecoratedComponent, which enabled a custom object
to be defined and then used in a SUPAPolicyClause
o SUPAPolicyCollection, which enables a collection of objects
to be gathered together and associated with all or a portion
of a SUPAPolicyClause
o SUPAECAComponet, which defines Events, Conditions, and Actions
as reusable objects
This approach facilitates the machine-driven construction of
policies. Note that this is completely optional; policies do not
have to use these constructs.
4.4. The Design of the GPIM
This section describes the overall design of the GPIM.
4.4.1. Structure of Policies
The GPIM defines a policy as a type of PolicyContainer. For this
version, only ECA Policy Rules will be described. However, it
should be noted that the mechanism described is applicable to
other types of policies (e.g., declarative) as well.
Recall that a PolicyContainer was defined as a special type of
container that provides at least the following three functions:
1. It uses metadata to define how its content is interpreted
2. It separates the content of the policy from the
representation of the policy
3. It provides a convenient control point for OAMP operations.
The first requirement is provided by the ability for any subclass
of Policy (the root of the information model) to aggregate one or
more concrete instances of a PolicyMetadata class. This is
explained in detail in section 5.2.2.
The second requirement is met by representing an ECA Policy as
having two parts: (1) a rule part and (2) components that make up
the rule. Since functional and declarative policies are not,
strictly speaking, "rules", the former is named PolicyStructure,
while the latter is named PolicyComponentStructure.
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The third requirement is met by the concrete subclasses of
PolicyStructure. Since they are PolicyContainers, they are made
up of the SUPAECAPolicyRule, its commponents, and any metadata
that applies to the PolicyContainer, the SUPAECAPolicyRule, and.or
any components of the SUPAECAPolicyRule. This provides optional
low-level control over any part of the SUPAECAPolicyRule.
The above requirements result in the design shown in Figure 4.
A SUPAHasPolicyMetadata A
+------------------+/ \ \+--------------------+
| SUPAPolicyObject | A -----------------------| SUPAPolicyMetadata |
+---------+--------+\ / /+--------------------+
I 0..n 0..n
I
I
+------+------------------------------------+
I I
A I A I
+--------+------------+ +------------------+-----------+
| SUPAPolicyStructure | | SUPAPolicyComponentStructure |
+--------+------------+ +-------------+----------------+
/ \ / \
I I
(subclasses representing (subclasses representing
different types of policies) different policy components)
Figure 4. Structure of a Policy
Note that aggregation in Figure 4 (named SUPAHasPolicyMetadata)
is realized as an association class, in order to manage which set
of Metadata can be aggregated by which SUPAPolicyObject. The
combination of these three functions enables a PolicyContainer
to define the behavior of how its constituent components will be
accessed, queried, stored, retrieved, and how they operate.
It is often necessary to construct groups of policies. The GPIM
follows [2] and [5], and uses the composite pattern [11] to
implement this functionality, as shown in Figure 5 below. There
are a number of advantages to using the composite pattern over a
simple relationship, as detailed in [11].
Figure 5 shows that SUPAPolicyStructure has two subclasses:
SUPAPolicyStructureComposite and SUPAPolicyStructureAtomic. The
former is used to represent groups of SUPAPolicyStructure objects
(i.e., groups of SUPAPolicyStructureAtomic and/or
SUPAPolicyStructureComposite objects), and the latter is used to
represent stand-alone Policy Rules.
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A
1..n +---------------------+
\| |
+--------------------------| SUPAPolicyStructure |
| SUPAHasPolicyStructure /| |
| +--------+------------+
| / \
| I
| I
| +---------------+--------------+
| I I
| C I A I
| 0..1 +------------+---------------+ +-----------+-------------+
| / \| | | |
+--- A |SUPAPolicyStructureComposite| |SUPAPolicyStructureAtomic|
\ /| | | |
+----------------------------+ +-------------------------+
Figure 5. The Composite Pattern Applied to SUPAPolicyStructure
The SUPAHasPolicyStructure aggregation says that if it is
instantiated, one or more SUPAPolicyStructure objects can be
contained in a SUPAPolicyStructureComposite. This works due to
inheritance. Since the SUPAPolicyStructure class is a superclass
of both SUPAPolicyStructureAtomic and SUPAPolicyStructureComposite,
a SUPAPolicyStructureComposite can contain either class. The
SUPAHasPolicyStructure aggregation is realized as an association
class, in order to manage which set of SUPAPolicyStructure objects
can be aggregated by which SUPAPolicyStructureComposite object.
(If a stand-alone policy rule is desired, then a concrete instance
of a SUPAPolicyStructureAtomic class is created; there is no need
to instantiate the SUPAHasPolicyStructure aggregation.)
SUPAPolicyStructureComposite is defined as a concrete class, so
that it can be directly instantiated and used without having to
subclass it. In contrast, the other five classes described in
Figures 3 and 4 are all defined as abstract. This helps simplify
the construction of the data model, because abstract classes cannot
be instantiated (rather, they are used to define characteristics
and behavior of the concepts they represent).
4.4.2. Representing an ECA Policy Rule
An ECA policy rule is a statement that consists of an event clause,
a condition clause, and an action clause. Any or all of these
clauses can be made into more complex Boolean statements. For
example, the SUPAPolicyClause: "(A AND B) OR NOT (C AND D))
consists of two clauses, "(A AND B)" and "(C OR D)", that are
combined together using the operators OR and NOT.
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A SUPAECAPolicyRule is defined (in the EPRIM) as an abstract
subclass of SUPAPolicyStructureAtomic, so that the composite
pattern can be applied to it.
A A
+---------------------------+ +------------------+
| SUPAPolicyStructureAtomic | | SUPAPolicyClause |
+---------+---------+-------+ +--------+----+----+
/ \ / \ 0..1 1..n / \ I
I A | I
I \ / | I
I | | I
I | SUPAHasPolicyClause | I
I +------------------------+ I
A I A I
+------+------------+ +----------+-------+
| SUPAECAPolicyRule | | SUPAPolicyClause |
+-------------------+ +------------------+
Figure 6. SUPAECAPolicyRule Aggregating SUPAPolicyClauses
Note that the aggregation SUPAHasPolicyClause in Figure 6 is
realized as an association class, in order to manage which set
of SUPAPolicyClauses can be aggregated by which set of
SUPAECAPolicyRules. This aggregation is defined at the
SUPAPolicyStructureAtomic level, and not at SUPAECAPolicyRule,
so that non-ECA policies can use this aggregation.
Since a SUPAECAPolicyRule consists of three SUPAPolicyClauses,
at least three separate instances of the SUPAHasPolicyClause
aggregation are instantiated in order to make a complete
SUPAECAPolicyRule, as shown in Figure 7.
A A
+-------------------+ +--------------------+
| SUPAECAPolicyRule | | SUPAPolicyClause |
+--+----+----+------+ +-------+----+----+--+
/ \ / \ / \ 1..n 0..n / \ / \ / \
A A A | | |
\ / \ / \ / | | |
| | | | | |
| | | SUPAHasPolicyClause #1 | | |
| | +------------------------------+ | |
| | | |
| | SUPAHasPolicyClause #2 | |
| +----------------------------------------+ |
| |
| SUPAHasPolicyClause #3 |
+--------------------------------------------------+
Figure 7. Instantiating a SUPAECAPolicyRule, part 1
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In figure 7, SUPAECAPolicyRule is shown as "owning" these three
aggregations, since it inherits them from its superclass
(SUPAPolicyStructureAtomic). The three aggregations represent the
event, condition, and action clauses of a policy rule. Note that
each of these clauses MAY consist of one or more
SUPAPolicyClauses. Similarly, each SUPAPolicyClause MAY
consist of one or more clauses. In this way, simple and complex
(e.g., Boolean combinations of clauses) are supported, without
having to define additonal objects (as is done in [RFC3460] and
[4], with the SimplePolicyCondition, CompoundPolicyCondition,
SimplePolicyAction, and CompoundPolicyAction classes).
The multiplicity of the SUPAHasPolicyClause aggregation is
1..n on the aggregate side and 0..n on the part side. This means
that a particular SUPAECAPolicyRule MUST have at least one
SUPAPolicyClause. This cardinality is refined to 3..n for
SUPAECAPolicyRules, but is defined to be 1..n because other
types of Policies have different needs. The 0..n cardinality
means that a SUPAPolicyClause may be aggregated by zero or
more SUPAECAPolicyRules. The zero is provided so that
SUPAPolicyClauses can be stored in a repository before the
SUPAECAPolicyRule is created; the "or more" recognizes the fact
that multiple SUPAECAPolicyRules could aggregate the same
SUPAPolicyClause.
In Figure 7, suppose that SUPAHasPolicyClause#1, #2, and #3
represent the aggregations for the event, condition, and action
clauses, respectively. This means that each of these
SUPAHasPolicyClause aggregations must explicitly identify the
type of clause that it represents.
In looking at Figure 7, there is no difference between any of the
three aggregations, except for the type of clause that the
aggregation represents (i.e., event, condition, or action clause).
Therefore, three different aggregations, each with their own
association class, is not needed. Instead, the GPIM defines a
single aggregation (SUPAHasPolicyClause) with a single abstract
association class (SUPAHasPolicyClauseDetail); this association
class is then subclassed into three concrete subclasses, one each
to represent the semantics for an event, condition, and action
clause. This is shown in Figure 8.
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A A
+-------------------+ +------------------+
| SUPAECAPolicyRule | | SUPAPolicyClause |
+---------+---------+ +----------+-------+
/ \ 1..n 0..n / \
A |
\ / |
| |
| SUPAHasPolicyClause |
+--------------+-----------------+
^
|
A |
+--------------+------------+
| SUPAHasPolicyClauseDetail |
+--------------+------------+
/ \
I
I
+----------------+-----------------------+
I I I
C I C I C I
+--------+-----+ +-------+----------+ +---------+-----+
|Event subclass| |Condition subclass| |Action subclass|
+--------------+ +------------------+ +---------------+
Figure 8. Instantiating a SUPAECAPolicyRule, part 2
The policy management system may use any number of different
software mechanisms, such as introspection or reflection, to
determine the nature of the aggregation, and select the
appropriate subclass of SUPAHasPolicyClauseDetail. The three
subclasses of SUPAHasPolicyClauseDetail are named
SUPAHasPolicyEventDetail, SUPAHasPolicyConditionDetail, and
SUPAHasPolicyActionDetail, respectively.
4.4.3. Creating SUPA Policy Clauses
There are two different types of Policy Components. They are a
SUPAPolicyClause and a SUPAPolicyComponentDecorator. The former
is used to construct SUPAECAPolicyRules. However, since each
SUPAECAPolicyRule can be made up of a variable number of
SUPAPolicyComponents, the decorator pattern is used to "wrap"
any concrete subclass of SUPAPolicyClause with zero or more
concrete subclasses of the PolicyComponentDecorator object.
This avoids problems of earlier models that resulted in a
proliferation of classes and relationships, and is shown in
Figure 9.
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A 1..n
+------------------------------+/
| SUPAPolicyComponentStructure |----------------------+
+------------------------------+\ |
/ \ |
I SUPAHasPolicyComponentDecorators |
I |
+--------------+-----------+ |
I I |
A I A I |
+---------+--------+ +--------------+---------------+ 0..1 |
| | | |/ \ |
| SUPAPolicyClause | | SUPAPolicyComponentDecorator | A -----+
| | | |\ /
+------------------+ +------------------------------+
Figure 9. Subclasses of SUPAPolicyComponentStructure
While the above looks like a composite pattern, it is actually
the decorator pattern [11]. As stated in 4.3, this pattern
enables behavior to be selectively added to an individual
object, either statically or dynamically, without affecting the
behavior of other objects from the same class. Zero or more
concrete subclasses of the SUPAPolicyComponentDecorator class
can be used to decorate, or "wrap", any of the concrete
subclasses of SUPAPolicyClause. Instead of using inheritance to
statically create new classes to represent new types of object,
the decorator pattern uses composition to dynamically combine
smaller objects into more robust ones. This is done by defining an
interface in SUPAPolicyComponent that all of the subclasses of
SUPAPolicyComponent conform to. Since the subclasses are of the
same type as SUPAPolicyComponent, they all have the same interface.
This allows each concrete SUPAPolicyComponentDecorator subclass to
add its attributes and/or behavior to the concrete subclass of
SUPAPolicyClause that it is decorating (or "wrapping").
More importantly, this represents an important design optimization
for data models. Note that a single SUPAECAPolicyRule can consist
of any number of SUPAPolicyClauses, each of very different
types. If inheritance was used, then a subclass AND an aggregation
would be required for each separate statement that makes up the
policy rule. Clearly, continuing to subclass is not practical.
Worse, suppose composite objects are desired (e.g., a new object
Foo is made up of existing objects Bar and Baz). If all that was
needed was one attribute of Bar and two of Baz, the developer
would still have to use the entire Bar and Baz classes. This is
wasteful and inefficient.
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In contrast, the decorator pattern enables all, or just some, of
the attributes and/or behavior of a class to "wrap" another class.
This is used heavily in many production systems (e.g., the
java.io package) because the result is only the behavior that is
required, and no other objects are affected.
This class hierarchy is used to define objects that may be used
to construct a SUPAPolicyClause. The decorator object can add
behavior before, and/or after, it delegates to the object that it
is decorating. The subclasses of SUPAPolicyComponentDecorator
provide a very flexible and completely dynamic mechanism to:
1) add or remove behavior to/from an object
2) ensure that objects are constructed using the minimum amount
of features and functionality required
SUPAPolicyComponentDecorator defines four subclasses, as shown in
Figure 10.
A
+----------------------------+
|SUPAPolicyComponentDecorator|
+-------------+--------------+
/ \
I
I
+------------+------------+-----------------+
I I I I
A I I C I I
+--------+-------+ I +--------+-------------+ I
| SUPAPolicyTerm | I | SUPAPolicyCollection | I
+----------------+ I +----------------------+ I
I I
C I A I
+---------------+--------------+ +---------+--------+
| SUPAVendorDecoratedComponent | | SUPAECAComponent |
+------------------------------+ +------------------+
Figure 10. Subclasses of SUPAPolicyComponentDecorator
If a SUPAPolicyEncodedClause is being used, then there is no need
to use any of the SUPAPolicyComponentDecorator subclasses, since
the SUPAPolicyEncodedClause already completely defines the
SUPAPolicyClause.
However, if a SUPAPolicyEncodedClause is NOT being used, then a
SUPA Policy Clause will be constructed using one or more types of
objects that are each subclasses of SUPAPolicyComponentDecorator.
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These four subclasses provide four different ways to construct a
SUPAPolicyClause:
1) as a {variable, operator, value} clause
2) as an encoded object (e.g., to pass YANG or CLI code)
3) as a collection of objects that requires further processing
in order to be made into a SUPAPolicyClause
4) as an Event, Condition, or Action object
The power of the decorator pattern is that these four different
types of objects can be intermixed. For example, the first and
last types can be combined as follows:
Variable == Event (A)
Condition BETWEEN VALUE1 and VALUE2 (B)
(Event.severity == 'Critical' AND
(SLA.violation == TRUE OR User.class == 'Gold')) (C)
In the above rules, example (B) defines two different instances of
a Value class, denoted as Value1 and Value2; (C) uses the
nomenclature foo.bar, where foo is the name of a class, and bar is
the name of an attribute of that class.
4.4.4. Creating SUPAPolicyClauses
The GPIM defines a single subclass of SUPAPolicyClause, called
SUPAPolicyEncodedClause. This clause is generic in nature, and
MAY be used with any type of policy (ECA or otherwise). The EPRIM
defines an ECA-specific subclass of the GPIM, called a
SUPAPolicyBooleanClause, which is intended to be used with just
ECA policy rules; however, other uses are also possible.
Together, the GPIM and EPRIM provide several alternatives to
implement a SUPAPolicyClause, enabling the developer to
optimize the solution for different constraints:
1) The policy statement can be encoded using one or more
SUPAPolicyEncodedClauses; this has the option of encoding
the entire statement or any of its three individual clauses
(event, condition, action).
2) The policy statement can be defined using one or more
SUPAPolicyBooleanClauses; each of the three clauses can be
defined as either a single SUPAPolicyBooleanClause, or a
combination of SUPAPolicyBooleanClauses that are logically
ANDed, ORed, and/or NOTed.
3) The above two mechanisms can be combined (e.g., the first
used to define the event clause, and the second used to
define the condition and action clauses).
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Figure 11 shows the subclasses of SUPAPolicyClause.
A
+------------------+
| SUPAPolicyClause |
+--------+---------+
/ \
I
I
I
+------------+------------+
I I
A I C I
+------------+----------+ +-----------+-----------+
|SUPAPolicyBooleanClause| |SUPAPolicyEncodedClause|
+-----------------------+ +-----------------------+
Figure 11. Subclasses of SUPAPolicyClause
SUPAPolicyBooleanClause is defined in the EPRIM, and is used to
construct Boolean clauses that collectively make up a
SUPAPolicyClause. It is abstract so that the composite pattern
can be applied to it, which enables hierarchies of Boolean
clauses to be created.
4.4.5. SUPAPolicySources
A SUPAPolicySource is a set of managed entities that authored,
or are otherwise responsible for, this SUPAPolicy. Note that a
SUPAPolicySource does NOT evaluate or execute SUPAPolicies. Its
primary use is for auditability, authorization policies, and
other applications of deontic and/or alethic logic.
SUPAPolicyStructure defines two aggregations, SUPAHasPolicySource
and SUPAHasPolicyTarget. Since SUPAECAPolicyRule is a subclass of
SUPAPolicyStructureAtomic, which is in turn a subclass of
SUPAPolicyStructure, it (and its subclasses) inherit both of
these aggregations. This enables SUPAPolicySources and/or
SUPAPolicyTargets to be attached to SUPAECAPolicyRules.
Figure 12 shows how SUPAPolicySources and SUPAPolicyTargets are
attached to a SUPAPolicy. Note that both of these aggregations
are defined as optional, since their multiplicity is 0..n - 0..n.
In addition, both of these aggregations are realized as
association classes, in order to be able to control which
SUPAPolicySources and SUPAPolicyTargets are attached to a given
SUPAECAPolicyRule.
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A
+------------------+
| SUPAPolicyObject |
+--------+---------+
/ \
I
I
I
+---------------+----+--------------------+
I I I
I I I
A I C I C I
+----------+--------+ +--------+-------+ +--------+-------+
|SUPAPolicyStructure| |SUPAPolicySource| |SUPAPolicyTarget|
+----------+--------+ +--------+-------+ +--------+-------+
/ \ 0..n / \ 0..n / \
I | |
I | |
I +--------+ |
I | SUPAHasPolicySource |
I | |
I / \ |
I A |
A I 0..n \ / |
+------------+--------------+ 0..n |
| |/ \ |
| SUPAPolicyStructureAtomic | A -----------------------+
| |\ / SUPAHasPolicyTarget
+------------+--------------+
/ \
I
I
A I
+---------+---------+
| SUPAECAPolicyRule |
+-------------------+
Figure 12. ECAPolicyRules, SUPAPolicySources, and PolicyTargets
A SUPAPolicySource MAY be mapped to a role (e.g., using the
role-object pattern [11]); this indirection makes the system less
fragile, as entities can be transparently added or removed from
the role definition without adversely affecting the definition of
the SUPAPolicy. Note that SUPAPolicyRole is a subclass of
SUPAPolicyMetadata.
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4.4.6. SUPAPolicyTargets
A SUPAPolicyTarget defines the set of managed entities that a
SUPAPolicy is applied to. This is useful for debugging, as well as
when the nature of the application requires the set of managed
entities affected by a Policy to be explicitly identified. This is
determined by two conditions:
1) The set of managed entities that are to be affected by the
SUPAPolicy must all agree to play the role of a
SUPAPolicyTarget. For example, a managed entity may or may
not be in a state that enables SUPAPolicies to be applied to
it to change its state.
2) A SUPAPolicyTarget must be able to:
a) process (either directly or with the aid of a proxy)
SUPAPolicies, and/or
b) receive the results of a processed SUPAPolicy and
apply those results to itself.
Figure 12 showed how SUPAPolicyTargets are attached to
SUPAECAPolicyRules.
A SUPAPolicyTarget MAY be mapped to a role (e.g., using the
role-object pattern [11]); this indirection makes the system less
fragile, as entities can be transparently added or removed from
the role definition without adversely affecting the definition of
the SUPAPolicy. Note that SUPAPolicyRole is a subclass of
SUPAPolicyMetadata.
4.4.7. Policy Metadata
Metadata is, literally, data about data. As such, it can be
descriptive or prescriptive in nature.
4.4.7.1. Motivation
There is a tendency in class design to make certain attributes,
such as description, status, validFor, and so forth, bound to a
specific class (e.g., [6]). This is bad practice in an information
model. For example, different classes in different parts of the
class hierarchy could require the use of any of these attributes;
if one class is not a subclass of the other, then they must each
define the same attribute as part of their class structure. This
makes it difficult to find all instances of the attribute and
ensure that they are synchronized. Furthermore, context can
dynamically change the status of an object, so an easy way to
update the status of one object instance without affecting other
instances of the same object is required.
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Many models, such as [4] and [6], take a simplistic approach of
defining a common attribute high in the hierarchy, and making it
optional. This violates classification theory, and defeats the
purpose of an information model, which is to specify the
differences in characteristics and behavior between classes (as
well as define how different classes are related to each other).
Note that this also violates a number of well-known software
architecture principles, including:
o the Liskov Substitution Principle [13]
(if A is a subclass of B, then objects instantiated from
class B may be replaced with objects instantiated from
class A WITHOUT ALTERING ANY OF THE PROGRAM SEMANTICS)
o the Single Responsibility Principle [14]
(every class should have responsibility over one, and only
one, part of the functionality provided by the program)
Most models use inheritance, not composition. The former is
simpler, but has some well-known problems. One is called "weak
encapsulaton", meaning that a subclass can use attributes and
methods of a superclass, but if the superclass changes, the
subclass may break. Another is that each time a new object is
required, a new subclass must be created. These problems are
indicative of the models in [RFC3460], [4], and [6].
Composition is an alternative that provides code that is easier to
use. This means that composition can provide data models that are
more resistant to change and easier to use. By using composition,
we can select just the metadata objects that are needed, instead
of having to rely on statically defined objects. We can even
create new objects from a set of existing objects through
composition. Finally, we can use the decorator pattern to select
just the attributes and behaviors that are required for a given
instance.
In [2] and [5], a separate metadata class hierarchy is defined to
address this problem. This document follows this approach.
4.4.7.2. Design Approach
The goal of the GPIM is to enable metadata to be attached to any
subclass of SUPAPolicyObject that requires it. Since this is a
system intended for policy-based management, it therefore makes
sense to be able to control which metadata is attached to which
policies dynamically (i.e., at runtime).
One solution is to use the Policy Pattern [1], [2], [6], [12].
This pattern was built to work with management systems whose
actions were dependent upon context. The Policy Pattern works as
follows:
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o Context is derived from all applicable system inputs (e.g.,
OAMP data from network elements, business goals, time of
day, geo-location, etc.).
o Context is then used to select a working set of Policies.
o Policies are then used to define behavior at various
control points in the system.
o One simple type of control point is an association class.
Since the association class represents the semantics of how
two classes are related to each other, then
o ECAPolicyRule actions can be used to change the attribute
values, methods, and relationships of the association
class
o This has the affect of changing how the two classes are
related to each other
o Finally, as context changes, the working set of policies
change, enabling the behavior to be adjusted to follow
changes in context (according to appropriate business goals
and other factors, of course) in a closed loop manner.
Conceptually, this is accomplished as shown in Figure 13 below.
Defines
+----------+ Behavior +------------+
| Policies +----------------+ | SUPAPolicy |
+----+-----+ 1..n | +------+-----+
0..n /|\ | / \ 0..n
| 1..n \|/ A
| +-----------+--------------+ \ /
| | SUPAPolicyMetadataDetail | |
| +-----------+--------------+ |
| Selects | |
| Policies | |
| +-------------------->+
/ \ Applies |
A Behavior |
0..n \ / \ / 0..n
+----+-----+ +--------+---------+
| Context | |SUPAPolicyMetadata|
+----------+ +------------------+
Figure 13. Context-Aware Policy Rules
Assume that the set of deployed Policies are SUPAECAPolicyRules.
Then, the actions of these SUPAECAPolicyRules will, for example,
change attribute values in the SUPAPolicyMetadataDetail
association class. This class represents the behavior of the
SUPAHasPolicyMetadata aggregation, which is used to define
which SUPAPolicyMetadata can be attached to which SUPAPolicy objet
in this particular context.
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By using the decorator pattern on PolicyMetadata, any number of
PolicyMetadata objects (or their attributes, etc.) can be wrapped
around a concrete subclass of PolicyMetadata. This is shown in
Figure 14 below.
A
+------------------+
| SUPAPolicyObject |
+--------+---------+
/ \ 0..n
A
\ /
| A
| 0..n +----------------+
| SUPAHasPolicyMetadata \| |
+-------------+-------------------| PolicyMetadata |
^ /| |
| +--+----+--------+
A | / \ / \ 1..n
+-------------+---------------+ I |
| SUPAHasPolicyMetadataDetail | I |
+-----------------------------+ I |
I |
C I |
+----------------------------+ I |
| | I |
| SUPAPolicyConcreteMetadata +IIIIII+ |
| | I |
+----------------------------+ I |
I |
A I |
+-----------------------------+ I |
| | I |
| SUPAPolicyMetadataDecorator +IIIIIII+ |
| | |
+----------------+------------+ |
/ \ 0..1 |
A |
\ / |
| |
| PolicyObjectHasMetadata |
+-------------------------+
Figure 14. SUPAPolicyMetadata Subclasses and Relationships
Policy, PolicyMetadata, and PolicyMetadataDecorator are abstract;
PolicyConcreteMetadata is concrete, and is the object that
instances of the PolicyMetadataDecorator subclasses are wrapped
around.
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4.4.7.3. Structure of SUPAPolicyMetadata
This section will be completed in the next revision of this
document.
4.5. Advanced Features
This section will be completed in the next revision of this
document.
4.5.1. Policy Grouping
This section will be completed in the next revision of this
document.
4.5.2. Policy Rule Nesting
This section will be completed in the next revision of this
document.
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5. GPIM Model
This section defines the classes, attributes, and relationships of
the GPIM.
5.1. Overview
The overall class hierarchy is shown in Figure 15.
(Class of another model that SUPA is integrating into)
|
+---SUPAPolicyObject (5.2)
| |
| +---SUPAPolicyStructure (5.3)
| | |
| | +---SUPAPolicyStructureAtomic (5.4)
| | |
| | +---SUPAPolicyStructureComposite (5.5)
| |
| +---SUPAPolicyComponentStructure (5.6)
| | |
| | +---SUPAPolicyClause (5.7)
| | | |
| | | +---SUPAEncodedClause (5.8)
| | |
| | +---SUPAPolicyComponentDecorator (5.9)
| | |
| | +---SUPAPolicyTerm (5.10)
| | | |
| | | +---SUPAPolicyVariable (5.11)
| | | |
| | | +---SUPAPolicyOperator (5.12)
| | | |
| | | +---SUPAPolicyValue (5.13)
| | |
| | +---SUPAVendorDecoratedComponent (5.14)
| | |
| | +---SUPAPolicyCollection (5.15)
| |
| +---SUPAPolicySource (5.16)
| |
| +---SUPAPolicyTarget (see Section 5.17)
|
+---SUPAPolicyMetadata (see Section 5.18)
|
+---SUPAPolicyConcreteMetadata (see Section 5.19)
|
+---SUPAPolicyMetadataDecorator (see Section 5.20)
Figure 15: Main Classes of the GPIM
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SUPAPolicy is the root of the SUPA class hierarchy. For
implementations, it is assumed that SUPAPolicy is subclassed from
a class from another model. In Figure 15, indentation represents
subclassing. Numbers after a class refer to the section that
defines the class.
Classes, attributes, and relationships that are marked as
"mandatory" MUST be part of a conformant implementation. Classes,
attributes, and relationships that are marked as "optional"
SHOULD be part of a conformant implementation.
Unless otherwise stated, all classes (and attributes) defined in
this section were abstracted from DEN-ng [2], and a version of
them are in the process of being added to [5].
5.2. The Abstract Class "SUPAPolicyObject"
This is a mandatory abstract class. Figure 16 shows the
SUPAPolicyObject class, and its four subclasses.
0..n 0..n
+----------------+/ \ \+------------------+
|SUPAPolicyObject| A ------------------------|SUPAPolicyMetadata|
+--------+-------+\ / SUPAHasPolicyMetadata /+------------------+
/ \
I
I
+-----------------+----------------+-----------+
I I I I
I I I I
+--------+------------+ I I I
| SUPAPolicyStructure | I I I
+---------------------+ I I I
I I I
+-----------------+------------+ I I
| SUPAPolicyComponentStructure | I I
+------------------------------+ I I
I I
+---------+--------+ I
| SUPAPolicyTarget | I
+------------------+ I
I
+----------+-------+
| SUPAPolicySource |
+------------------+
Figure 16. SUPAPolicyObject and Its Subclasses
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This class is the root of the SUPA class hierarchy. It defines the
common attributes and relationships that all SUPA subclasses
inherit.
A SUPAPolicyObject MAY be qualified by a set of zero or more
SUPAPolicyMetadata objects. This is provided by the
SUPAHasPolicyMetadata aggregation (see Section 5.2.2). This
enables the semantics of the SUPAPolicyObject to be more
completely specified.
5.2.1. SUPAPolicyObject Attributes
This section defines the attributes of the SUPAPolicyObject class.
These attributes are inherited by all subclasses of the GPIM
except for the SUPAPolicyMetadata class, which is a sibling class.
5.2.1.1. Object Identifiers
This document defines two class attributes in SUPAPolicyObject,
called supaPolObjIDContent and supaPolObjIDFormat, that together
define a unique object ID. This enables all class instances to be
uniquely identified.
One of the goals of SUPA is to be able to generate different data
models that support different types of protocols and repositories.
This means that the notion of an object ID must be generic. It is
inappropriate to use data modeling concepts, such as keys, GUIDs,
UUIDs, FQDNs, URIs, and other similar mechanisms, to define the
structure of an information model. Therefore, a synthetic object
ID is defined using these two attributes. This can be used to
facilitate mapping to different data model object schemes, such
as those depending on URIs, FQDNs, UUIDs, primary key-foreign key
relationships, UUIDs, and others can all be accommodated.
The two attributes work collectively, with one defining the
content of the object ID and the other defining how to interpret
the content. These two attributes form a tuple, and together
enable a machine to understand the syntax and value of an object
identifier for the object instance of this class. This is based on
the DEN-ng class design [2].
Similarly, all SUPA classes are attributes are both uniquely
named as well as prepended with the prefixes "SUPA" and "supa",
respectively, to facilitate model integration.
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5.2.1.2. The Attribute "supaPolObjIDContent"
This is a mandatory string attribute that represents part of the
object identifier of an instance of this class. It defines the
content of the object identifier. It works with another class
attribute, called supaPolObjIDFormat, which defines how to
interpret this attribute. These two attributes form a tuple,
and together enable a machine to understand the syntax and value
of an object identifier for the object instance of this class.
This is based on the DEN-ng class design [2].
5.2.1.3. The Attribute "supaPolObjIDFormat"
This is a mandatory non-zero enumerated integer attribute that
represents part of the object identifier of an instance of this
class. It defines the format of the object identifier. It works
with another class attribute, called supaPolObjIDContent, which
defines the content of the object ID. These two attributes form
a tuple, and together enable a machine to understand the syntax
and value of an object identifier for the object instance of
this class. The supaPolObjIDFormat attribute is mapped to the
following values:
0: undefined
1: GUID
2: UUID
3: primary key
4: foreign key
5: URI
6: FQDN
The value 0 may be used to initialize the system, or to signal
that there is a problem with thius particular SUPAPolicyObject.
5.2.1.4. The Attribute "supaPolicyDescription"
This is an optional string attribute that defines a free-form
textual description of this object.
5.2.1.5. The Attribute "supaPolicyName"
This is an optional string attribute that defines the name of this
Policy. This enables any existing generic naming attribute to be
used for generic naming, while allowing this attribute to be used
to name Policy entities in a common manner. Note that this is NOT
the same as the commonName attribute of the Policy class defined
in RFC3060 [RFC3060], as that attribute is intended to be used
with just X.500 cn attributes.
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5.2.2. SUPAPolicy Relationships
This section defines the relationships of the SUPAPolicy class.
5.2.2.1. The Aggregation "SUPAHasPolicyMetadata"
This is a mandatory aggregation that defines the set of
SUPAPolicyMetadata that are aggregated by this particular
SUPAPolicyObject.
This aggregation is defined in section 5.18.2
5.2.2.2. The Association Class "SUPAHasPolicyMetadataDetail"
This is a mandatory concrete association class that defines the
semantics of the SUPAPolicyMetadata aggregation. This enables the
attributes and relationships of the SUPAPolicyMetadataDetail class
to be used to constrain which SUPAPolicyMetadata objects can be
aggregated by this particular SUPAPolicyObject instance.
This association class is defined in Section 5.18.3.
5.3. The Abstract Class "SUPAPolicyStructure"
This is a mandatory abstract class that is used to represent the
structure of a SUPAPolicy. This class (and all of its subclasses)
is a type of PolicyContainer. SUPAPolicyStructure was abstracted
from DEN-ng [2], and a version of this class is in the process of
being added to [5]. For this release, the only official type of
rule that is supported is the event-condition-action (ECA) type
of policy rule. However, the structure of the SUPA hierarchy is
defined to facilitate adding new types of rules.
A SUPAPolicy may take the form of an individual policy or a set
of policies. This requirement is supported by applying the
composite pattern to the SUPAPolicyStructure class, as shown in
Figure 5. Two subclasses of SUPAPolicyStructure are defined:
SUPAPolicyAtomic (for defining stand-alone policies) and
SUPAPolicyComposite (for defining hierarchies of policies). Each
SSUPAPolicyComposite can have zero or more instances of a concrete
subclass of a SUPAPolicyAtomic class and/or a SUPAPolicyComposite
class, or subclasses of either.
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5.3.1. SUPAPolicyStructure Attributes
This section defines the attributes of the SUPAPolicyStructure
class. Care must be taken in adding attributes to this class,
because the behavior of future subclasses of this class (e.g.,
declarative and functional policies) is very different than the
behavior of SUPAECAPolicyRules.
5.3.1.1. The Attribute "supaPolContinuumLevel"
This is an optional non-negative integer attribute. It defines
the level of abstraction, or policy continuum level [10], of this
particular SUPAPolicy. The value assignment of this class is
dependent on the application; however, it is recommended that
for consistency with other SUPA attributes, the value of 0 is
reserved for initialization and/or error conditions.
By convention, lower values represent more abstract levels of the
policy continuum. For example, a value of 1 could represent
business policy, a value of 2 could represent application-specific
policies, and a value of 3 could represent low=level policies for
network administrators.
5.3.1.2. The Attribute "supaPolDeployStatus"
This is an optional attribute, which is an enumerated,
non-negative integer. It defines the current deployment status of
this SUPAPolicy. This means that both individual and groups of
policies may be deployed. Both operational and test mode values
are included in its definition. Values include:
0: undefined
1: deployed and enabled
2: deployed and in test
3: deployed but not enabled
4: ready to be deployed
5: not deployed
5.3.2. SUPAPolicyStructure Relationships
The SUPAPolicyStructure class owns two relationships, which are
defined in the following two subsections.
5.3.2.1. The Aggregation "SUPAHasPolicySource"
This is an optional aggregation, and defines the set of
SUPAPolicySource objects that are attached to this particular
SUPAPolicyStructure object. The semantics of this aggregation
are defined by the SUPAHasPolicySourceDetail association class.
PolicySource objects are used for authorization policies, as well
as to enforce deontic and alethic logic.
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5.3.2.2. The Association Class "SUPAHasPolicySourceDetail"
This is an optional association class, and defines the semantics
of the SUPAHasPolicySource aggregation. The attributes and
relationships of this class can be used to define which
SUPAPolicySource objects can be attached to which particular set
of SUPAPolicyStructure objects.
Attributes will be added to this class at a later time.
5.3.2.3. The Aggregation "SUPAIsTargetOf"
This is an optional aggregation, and defines the set of
SUPAPolicyTargets that are attached to this particular
SUPAPolicyStructure. The semantics of this aggregation is
defined by the SUPAIsTargetOfDetail association class. The
purpose of this class is to explicitly identify managed objects
that will be affected by the execution of one or more SUPAPolicies.
5.3.2.4. The Association Class "SUPAIsTargetOfDetail"
This is an optional association class, and defines the semantics
of the SUPAPolicyTargetOf aggregation. The attributes and
relationships of this class can be used to define which
SUPAPolicyTargets can be attached to which particular set of
SUPAPolicyStructure objects.
Attributes will be added to this class at a later time.
5.4. The Abstract Class "SUPAPolicyStructureAtomic"
SUPAPolicyStructureAtomic is the superclass of all of the different
types of policies supported by the GPIM. For this release of this
document, this is limited to ECA policy rules.
The purpose of the SUPAPolicyStructureAtomic class is to provide a
control point for aggregating SUPAPolicyClauses. Since it is the
superclass of each type of policy, this means that all policies
will use this same, critical, abstraction.
A SUPAPolicyStructureAtomic represents a complete policy. More
specifically, a SUPAPolicyStructureAtomic class represents a
SUPAPolicy that can operate as a single, stand-alone, manageable
object. Put another way, a SUPAPolicyStructureAtomic object can NOT
be modeled as a set of hierarchical SUPAPolicy objects; if this
functionality is required, then at least one
SUPAPolicyStructureComposite object MUST be used.
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Each SUPAPolicyStructureAtomic object (or a subclass of it) MUST
have at least one SUPAPolicyClause that is used to define the
content of the policy.
A SUPAPolicyStructureAtomic SHOULD have one or more instances of
SUPAPolicyMetadata attached to it, so that the SUPAPolicyMetadata
may provide additional descriptive and prescriptive information
about the SUPAPolicyStructureAtomic object. It MAY also have one
or more SUPAPolicySources and/or SUPAPolicyTargets attached to it.
SUPAPolicyStructureAtomic objects inherit the attributes defined
for its parent class (SUPAPolicyStructure). For example, they can
be deployed, and have an associated policy continuum level.
5.4.1. SUPAPolicyStructureAtomic Attributes
This section defines the attributes of the
SUPAPolicyStructureAtomic class. This class defines the behavior
of all types of atomic (i.e., stand-alone) policies, not just
ECA policy rules. Therefore, care must be taken in adding
attributes to this class, because the behavior of future
subclasses of this class (e.g., declarative and functional
policies) is very different than the behavior of
SUPAECAPolicyRules.
5.4.1.1. The Attribute "supaPolExecStatus"
This is an optional attribute, which is an enumerated,
non-negative integer. It defines the current execution status
of this SUPAPolicy. Both operational and test mode values are
included in its definition. Values include:
0: undefined
1: executed and SUCEEDED (operational mode)
2: executed and FAILED (operational mode)
3: currently executing (operational mode)
4: ready to execute (operational mode)
5: executed and SUCEEDED (test mode)
6: executed and FAILED (test mode)
7: currently executing (test mode)
8: ready to execute (test mode)
5.4.1.2. The Attribute "supaPolExecFailStrategy"
This is an optional non-negative, enumerated integer that defines
what actions, if any, should be taken by this
SUPAPolicyStructureAtomic object if it fails to execute correctly.
Values include:
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0: undefined
1: attempt rollback of all actions taken and stop execution
2: attempt rollback of only the action that failed and stop
execution
3: stop execution but do not rollback any policies
4: ignore failure and continue execution
A value of 0 can be used as an error condition. A value of 1 means
that ALL execution is stopped, rollback of all actions (whether
successful or not) is attempted, and that SUPAPolicies that
otherwise would have been executed are ignored. A value of 2 means
that execution is stopped, and a rollback of that SUPAPolicy (and
ONLY that SUPAPolicy) is attempted. A value of 3 means that
execution is stopped, but any SUPAPolicies that have been
previously executed are left in their current state. A value of 4
means that any failure will be ignored, and execution continues.
5.4.1.3. The Attribute "supaPolExecFailTakeActionName"
This is an optional string attribute that identifies the name of
the remediation to take if this PolicyStructure object failed to
execute properly. The interpreation of this string attribute is
defined by the supaPolExecFailTakeActionRes class attribute.
5.4.1.4. The Attribute "supaPolExecFailTakeActionRes"
This is an optional enumerated, non-negative integer attribute that
defines how to interpet the value of the
supaPolExecFailTakeActionName class attribute. Values include:
0: undefined
1: by regex (regular expression)
2: by URI
*************************************************************
* *
* Editor's note: the above two attributes will be moved to *
* an association class, and an association will be defined *
* to make this more portable and powerful. *
* *
*************************************************************
5.4.2. SUPAPolicyStructureAtomic Relationships
The SUPAPolicyStructureAtomic class defines a single relationship
(SUPAHasPolicyClause), which is described in the following
subsection.
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5.4.2.1. The Aggregation "SUPAHasPolicyClause"
This is a mandatory aggregation that defines the set of
SUPAPolicyClauses that are aggregated by this particular
SUPAPolicyStructureAtomic instance. The semantics of this
aggregation are defined by the SUPAHasPolicyClauseDetail
association class.
Every SUPAPolicyStructureAtomic object instance MUST aggregate at
least one SUPAPolicyClause object instance. However, the
converse is NOT true. For example, a SUPAPolicyClause could be
instantiated and then stored for later use in a policy repository.
Furthermore, the same SUPAPolicyClause could be used by zero or
more SUPAPolicyStructureAtomic object instances.
Thus, the multiplicity of this aggregation is defined as 0..1 on
the aggregate (i.e., the SUPAPolicyStructureAtomic side) and 1..n
on the part (i.e., the SUPAPolicyClause side). This means that
at least one SUPAPolicyClause MUST be aggregated by this
SUPAPolicyStructureAtomic object. Similarly, a SUPAPolicyClause
may be aggregated by this particular SUPAPolicyStructureAtomic
object.
5.4.2.2. The Association Class "SUPAHasPolicyClauseDetail"
This is a mandatory association class, and defines the semantics
of the SUPAHasPolicyClause aggregation. The attributes and/or
relationships of this association class can be used to determine
which SUPAPolicyClauses are aggregated by which
SUPAPolicyStructureAtomic objects.
Attributes will be added to this class at a later time.
5.5. The Concrete Class "SUPAPolicyStructureComposite"
This is a mandatory concrete class. This class is a type of
PolicyContainer.
A SUPAPolicyStructureComposite class represents a SUPAPolicy as a
hierarchy of Policy objects, where the hierarchy contains
instances of SUPAPolicyStructureAtomic and/or
SUPAPolicyStructureComposite objects. Each of the SUPAPolicy
objects, including the outermost SUPAPolicyStructureComposite
object, are separately manageable. More importantly, the
SUPAPolicyStructureComposite object can aggregate any
SUPAPolicyStructure subclass.
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A SUPAPolicyStructureComposite SHOULD have one or more instances of
SUPAPolicyMetadata attached to it, so that the SUPAPolicyMetadata
may provide additional descriptive and prescriptive information
about the SUPAPolicyStructureComposite object. It MAY also have one
or more SUPAPolicySources and/or SUPAPolicyTargets attached to it.
5.5.1. SUPAPolicyStructureComposite Attributes
No attributes are currently defined for this class, as it
functions as a pure PolicyContainer.
Note that there is no need for a "match strategy attribute" that
some models [RFC3460], [4], [6] have; this is because this class
is just used for containment. Hence, the containers themselves
serve as the scoping component for nested policies.
5.5.2. SUPAPolicyStructureComposite Relationships
One relationship is currently defined for this class, and is
described in the following subsection.
5.5.2.1. The Aggregation "SUPAHasPolicy"
This is a mandatory aggregation that defines the set of
SUPAPolicyStructure objects that are aggregated by this
SUPAPolicyStructureComposite instance. The semantics of this
aggregation are defined by the SUPAHasPolicyDetail
association class.
5.5.2.2. The Association Class "SUPAHasPolicyDetail"
This is a mandatory association class, and defines the semantics
of the SUPAHasPolicy aggregation. The attributes and/or
relationships of this association class can be used to determine
which SUPAPolicyStructure objects are aggregated by which
SUPAPolicyStructureComposite objects.
Attributes will be added to this class at a later time.
5.6. The Abstract Class "SUPAPolicyComponentStructure"
This is a mandatory abstract class that is the superclass of all
objects that represent different types of components of a
SUPAPolicy. Different types of policies have different types of
structural components. However, all of these are used in at least
one type of policy. This class represents a convenient control
point for defining characteristics and behavior that are common
to objects that serve as components of a policy.
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5.6.1. SUPAPolicyComponentStructure Attributes
The SUPAPolicyComponentStructure currently defines two attributes;
these are defined in the following subsections.
5.6.1.1. The Attribute "supaAllowsExternalAccess"
This is a Boolean attribute. If its value is TRUE, then external
Applications can access and update the values of this
SUPAPolicyComponentStructure object. This enables Applications to
have controlled updating of policy components.
5.6.1.2. The Attribute "supaAllowsExternalUpdate"
This is a Boolean attribute. If its value is TRUE, then external
Applications can access (but not update) the values of this
SUPAPolicyComponentStructure object. This enables Applications to
have controlled access to policy components.
5.6.2. SUPAPolicyComponentStructure Relationships
No relationships are currently defined for this class.
5.7. The Abstract Class "SUPAPolicyClause"
This is a mandatory abstract class that separates the
representation of a SUPAPolicy from its implementation. This
abstraction is missing in [RFC3060], [RFC3460], [4], and [6].
A SUPAPolicyClause contains an individual or group of related
functions that are used to define the content of a policy. More
specifically, since the number and type of functions that make up
a SUPAPolicyClause can vary, the decorator pattern is used, so
that the contents of a SUPAPolicyClause can be adjusted
dynamically at runtime without affecting other objects.
This document defines two different types of policies: ECA policy
rules and encoded policies. Both use SUPAPolicyClauses.
SUPAPolicyClauses are objects in their own right, which
facilitates their reuse. SUPAPolicyClauses can aggregate a set
of any of the subclasses of SUPAPolicyComponentDecorator, which
was shown in Figure 10. These four subclasses provide four
different ways to construct a SUPAPolicyClause:
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1) as a {variable, operator, value} clause
2) as an encoded object (e.g., to pass YANG or CLI code)
3) as a collection of objects that requires further processing
in order to be made into a SUPAPolicyClause
4) as an Event, Condition, or Action object
SUPAPolicyClauses are aggregated by a SUPAPolicyStructureAtomic
object, which enables all types of SUPAPolicies to uniformly be
made up of one or more SUPAPolicyClauses.
5.7.1. SUPAPolicyClause Attributes
This section defines the attributes of the SUPAPolicyClause
class. These attributes are inherited by all subclasses of the
SUPAPolicyClause class.
5.7.1.1. The Attribute "supaPolStmtAdminStatus"
This is an optional attribute, which is an enumerated non-negative
integer. It defines the current administrative status of this
SUPAPolicyClause.
This attribute can be used to place this particular
SUPAPolicyClause into a specific administrative state, such as
enabled, disabled, or in test.
Note that since a SUPAPolicy is made up of SUPAPolicyClauses,
this enables all or part of a SUPAPolicy to be administratively
controlled. Values include:
0: Unknown (an error state)
1: Enabled
2: Disabled
3: In Test (i.e., no operational traffic can be passed)
Value 0 denotes an error that prevents this SUPAPolicyClause
from being used. Values 1 and 2 mean that this SUPAPolicyClause
is administratively enabled or disabled, respectively. A value of
3 means that this SUPAPolicyClause is in a special test mode and
SHOULD NOT be used as part of an OAM&P policy.
5.7.1.2. The Attribute "supaPolStmtExecStatus"
This is an optional attribute, which is an enumerated non-negative
integer. It defines whether this SUPAPolicyClause is currently
in use and, if so, what its execution status is.
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This attribute can be used to place this particular
SUPAPolicyClause into a specific execution state, such as
enabled, disabled, or in test. Values include:
0: Unknown (an error state)
1: Completed (i.e., successfully executed, but now idle)
2: Working (i.e., in use and no errors reported)
3: Not Working (i.e., in use, but errors have been reported)
4: In Test (i.e., cannot be used as part of an OAM&P policy)
5: Available (i.e., could be used, but currently isn't)
6: Not Available (i.e., not available for use)
Value 0 denotes an error that prevents this SUPAPolicyClause
from being used. Value 1 means that this SUPAPolicyClause has
successfully finished execution, and is now idle. Value 2 means
that this SUPAPolicyClause is in use; in addition, this
SUPAPolicyClause is working correctly. Value 3 is the same as
value 2, except that this SUPAPolicyClause is not working
correctly. Value 4 means that this SUPAPolicyClause is in a
special test state. A test state signifies that it SHOULD NOT be
used to evaluate OAM&P policies. Value 5 means that this
SUPAPolicyClause is available, but not currently in use. A
value of 6 means that it is unavailable for use.
5.7.2. SUPAPolicyClause Relationships
This class does not currently define any relationships, since the
decorator pattern is used to "wrap" this object with instances of
the subclasses of the SUPAPolicyComponentDecorator object.
5.8. The Concrete Class "SUPAEncodedClause"
This is a mandatory concrete class that refines the behavior of a
SUPAPolicyClause.
This class defines a generalized extension mechanism for
representing SUPAPolicyClauses that have not been modeled
with other SUPAPolicy objects. Rather, the contents of the policy
statement are directly encoded into the attributes of the
SUPAEncodedClause. Note that other subclasses of
SUPAPolicyClause use SUPAPolicy objects to define their
content. This class provides the developer a tradeoff of
efficiency vs. reusability.
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This class uses two of its attributes (supaPolicyClauseContent and
supaPolicyClauseFormat) for defining the content and format of a
vendor-specific policy statement. This allows direct encoding of
the policy statement, without having the "overhead" of using other
objects. However, note that while this method is efficient, it
does not reuse other SUPAPolicy objects. Rather, it can be thought
of as a direct encoding of the policy statement.
5.8.1. SUPAEncodedClause Attributes
This section defines the attributes of the SUPAEncodedClause class.
5.8.1.1. The Attribute "supaClauseContent"
This is a mandatory string attribute, and defines the content of
this encoded clause of this clause. It works with another attribute
of the SUPAEncodedClause class, called supaClauseFormat, which
defines how to interpret this attribute. These two attributes form
a tuple, and together enable a machine to understand the syntax and
value of the encoded clause for the object instance of this class.
5.8.1.2. The Attribute "supaClauseFormat"
This is a mandatory string attribute, and defines the format of
this encoded clause. It works with another attribute of the
SUPAEncodedClause class, called supaClauseContent, which
defines the content (i.e., the value) of the encoded clause. These
two attributes form a tuple, and together enable a machine to
understand the syntax and value of the encoded clause for the
object instance of this class.
5.8.1.3. The Attribute "supaClauseResponse"
This is an optional Boolean attribute that emulates a Boolean
response of this clause, so that it may be combined with other
subclasses of the SUPAPolicyClause that provide a status as to
their correctness and/or evaluation state. This enables this
object to be used in more complex Boolean policy clauses.
5.8.2. SUPAEncodedClause Relationships
This class currently does not define any relationships.
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5.9. The Abstract Class "SUPAPolicyComponentDecorator"
This is a mandatory aggregation, and is used to implement the
decorator pattern. The decorator pattern enables all or part of one
or more objects to "wrap" another concrete object. In SUPA, this
means that any concrete subclass of SUPAPolicyClause is wrapped
by any concrete subclass of SUPAPolicyComponentDecorator, as shown
in Figure 17 below.
A
+------------------------------+ 1..n
| |/
| SUPAPolicyComponentStructure |--------+
| |\ | used to wrap
+------------------------------+ | concrete
/ \ | subclasses
I | of
I | PolicyStmt
I |
+---------------+---------------+ / \
I I A
A I A I \ / 0..1
+----------+---------+ +--------------+-------+-------+
| SUPAPolicyClause | | SUPAPolicyComponentDecorator |
+----------+---------+ +--------------+---------------+
I I
I I
I I
Concrete Subclasses, Concrete Subclasses
(e.g., SUPAEncodedClause) (e.g., SUPAPolicyCollection)
(object being wrapped) (wrapping object(s))
Figure 17. The PolicyComponent Decorator Pattern
5.9.1. The Decorator Pattern
Each SUPAPolicyComponentDecorator object HAS_A (i.e., wraps) a
concrete instance of the SUPAPolicyClause object. This means that
the SUPAPolicyComponentDecorator object has an instance variable
that holds a reference to a SUPAPolicyClause object. Since the
SUPAPolicyComponentDecorator object has the same interface as the
SUPAPolicyClause object, the SUPAPolicyComponentDecorator object
(and all of its subclasses) are transparent to clients of the
SUPAPolicyClause object (and its subclasses).
Even better, this means that SUPAPolicyComponentDecorator object
instances can add attributes and/or methods to those of the concrete
instance of the chosen subclass of SUPAPolicyClause.
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Figure 18 shows how this is done for methods. 18a shows the initial
object to be wrapped; 18b shows SUPAPolicyCollection wrapping
SUPAEncodedClause; 18c shows SUPAVendorDecoratedComponent wrapping
SUPAPolicyCollection. When eval() is called in the outermost object
(SUPAVendorDecoratedComponent), it delegates to the eval() method
of SUPAPolicyCollection, which in turn delegates to the eval()
method of SUPAEncodedClause. This method executes and returns the
results to SUPAPolicyCollection, which executes and returns the
results to SUPAVendorDecoratedComponent, which executes and returns
the final result.
+-------------------+
| SUPAEncodedClause |
| eval() |
+-------------------+
(a) Initial Object
===>
+------------------------+
| SUPAPolicyCollection |
| eval() |
| +-------------------+ |
| | SUPAEncodedClause | |
| | eval() | |
| +-------------------+ |
+------------------------+
(b) SUPAPolicyCollection "wraps" SUPAEncodedClause
===>
+------------------------------+
| SUPAVendorDecoratedComponent |
| eval() |
| +-----------------------+ |
| | SUPAPolicyCollection | |
| | eval() | |
| | +-------------------+ | |
| | | SUPAEncodedClause | | |
| | | eval() | | |
| | +-------------------+ | |
| +-----------------------+ |
+------------------------------+
(c) SUPAVendorDecoratedComponent "wraps" SUPAPolicyCollection
Figure 18. Conceptual Depiction of eval() Decorated Method
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5.9.2. SUPAPolicyComponentDecorator Attributes
Currently, there are two attributes defined for this class, which
are described in the following subsections. Both attributes are
used by subclasses to constrain the behavior of that subclass;
they do **not** affect the relationship between the concrete
subclass of SUPAPolicyComponentDecorator that is wrapping the
concrete subclass of SUPAPolicyClause. This is different
than the use of similar attributes defined in the
SUPAHasDecoratedPolicyComponentDetail association class (which
are used to constrain the relationship between the concrete
subclass of SUPAPolicyClause and the concrete subclass of the
SUPAHasDecoratedPolicyComponent object that is wrapping it).
5.9.2.1. The Attribute "supaPolCompConstraintEncoding"
This is an optional non-negative enumerated integer that defines
how to interpret each string in the supaPolCompConstraint class
attribute. Values include:
0: undefined
1: OCL 2.4
2: OCL 2.x
3: OCL 1.x
4: QVT 1.2 - Relations Language
5: QVT 1.2 - Operational language
6: Alloy
The latest version of OCL is 2.4, but since this is considered by
most the default language for specifying constraints, enumerations
1-3 are dedicated to OCL. QVT defines a set of languages; the two
most powerful and useful are defined by enumerations 4 and 5.
Alloy is a language for describing constraints, and uses a SAT
solver to guarantee correctness.
5.9.2.2. The Attribute "supaAPolCompConstraint[0..n]"
This is an optional array of string attributes. Each attribute
specifies a constraint to be applied using OCL 2.0. This provides
a more rigorous and flexible treatment of constraints than is
possible in [RFC3460]. Each string attribute is interpreted
according to the value of the supaPolCompConstraintEncoding
class attribute.
5.9.3. SUPAPolicyComponentDecorator Relationships
One relationship is currently defined for this class, which is
described in the following subsection.
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5.9.3.1. The Aggregation "SUPAHasDecoratedPolicyComponent"
This is a mandatory aggregation, and is part of a decorator
pattern. It is used to enable a concrete instance of a
SUPAPolicyComponentDecorator to dynamically add behavior to a
specific type of SUPAPolicyClause object. The semantics of this
aggregation are defined by the
SUPAHasDecoratedPolicyComponentDetail association class.
5.9.3.2. The Association Class
"SUPAHasDecoratedPolicyComponentDetail"
This is a mandatory concrete association class, and defines the
semantics of the SUPAHasDecoratedPolicyComponent aggregation. The
purpose of this class is to use the Decorator pattern to determine
which SUPAPolicyComponentDecorator object instances, if any, are
required to augment the functionality of the concrete subclass of
SUPAPolicyClause that is being used.
Currently, there are two attributes defined for this class, which
are described in the following subsections. Both attributes are
used in this association class (and its associated aggregation)
to constrain the **relationship** between the concrete subclass
of SUPAPolicyComponentDecorator that is wrapping the concrete
subclass of SUPAPolicyClause; in contrast, class attributes of
SUPAPolicyComponentDecorator (see section 5.9.2) only affect that
specific subclass.
5.9.3.2.1. The Attribute "supaDecoratedConstraintsEncoding"
This is a non-negative enumerated integer that defines how to
interpret each string in the supaDecoratedConstraints class
attribute. Values include:
0: undefined
1: OCL 2.4
2: OCL 2.x
3: OCL 1.x
4: QVT 1.2 - Relations Language
5: QVT 1.2 - Operational language
6: Alloy
The latest version of OCL is 2.4, but since this is considered by
most the default language for specifying constraints, enumerations
1-3 are dedicated to OCL. QVT defines a set of languages; the two
most powerful and useful are defined by enumerations 4 and 5.
Alloy is a language for describing constraints, and uses a SAT
solver to guarantee correctness.
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5.9.3.2.2. The Attribute "supaDecoratedConstraints[0..n]"
This is an optional array of string attributes. Its purpose is to
collect a set of constraints to be applied to a decorated object.
The interpretation of each constraint in the array is defined in
the supaDecoratedConstraintsEncoding class attribute.
5.9.4. Illustration of Constraints in the Decorator Pattern
The following example will illustrate how the different constraints
defined in sections 5.9.2 (class attribute constraints) and section
5.9.3 (relationship constraints) can be used.
Figure 19 builds a simple SUPAPolicyClause that has both types
of relationships.
A A
+---------+--------+ 0..1 1..n +--------------+-------------+
| |/ \ \| |
|vSUPAPolicyClausev| A ------+-----|SUPAPolicyComponentDecorator|
| |\ / ^ /| |
+---------+--------+ | +--------------+-------------+
I | I
C I | C I
+--------+--------+ | +---------+----------+
|SUPAEncodedClause| | |SUPAPolicyCollection|
+-----------------+ | +--------------------+
|
C |
+------------------+------------------+
|SUPAHasDecoratedPolicyComponentDetail|
+-------------------------------------+
Figure 19. Constraints in the Decorator Pattern
Figure 19 says that a SUPAPolicyClause, realized as a
SUPAEncodedClause, is wrapped by a SUPAPolicyCollection object.
The attributes in the SUPAPolicyComponentDecorator object are used
to constrain the attributes in the SUPAPolicyCollection object,
while the attributes in the SUPAHasDecoratedPolicyComponentDetail
object are used to contrain the behavior of the aggregation
(SUPAHasDecoratedPolicyComponent). For example, the attributes in
the SUPAPolicyComponentDecorator object could restrict the data
type and range of the components in the SUPAPolicyCollection, while
the attributes in the SUPAHasDecoratedPolicyComponentDetail object
could restrict which SUPAPolicyCollection objects are allowed to be
used with which SUPAEncodedClauses.
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5.10. The Abstract Class "SUPAPolicyTerm"
This is a mandatory abstract class that is the parent of
SUPAPolicy objects that can be used to define a standard way to
test or set the value of a variable. It does this by defining a
3-tuple, in the form {variable, operator, value}, where each
element of the 3-tuple is defined by a concrete subclass of the
appropriate type (i.e., SUPAPolicyVariable, SUPAPolicyOperator,
and SUPAPolicyValue classes, respectively). For example, a
generic test or set of the value of a variable is expressed as:
{variable, operator, value}.
A class diagram is shown in Figure 20.
A
+----------------+
| SUPAPolicyTerm |
+--------+-------+
/ \
I
I
I
+-----------------+---+--------------------+
I I I
I I I
C I C I C I
+--------+---------+ +--------+---------+ +-------+-------+
|SUPAPolicyVariable| |SUPAPolicyOperator| |SUPAPolicyValue|
+------------------+ +------------------+ +---------------+
Figure 20. SUPAPolicyTerm Class Hierarchy
Note that generic test and set expressions do not have to only use
objects that are subclasses of SUPAPolicyTerm. For example, the
polVendorDecoratedContent attribute of the
SUPAVendorDecoratedComponent could be used as the variable (or the
value) term of a get or set expression.
Hence, the utility of the subclasses of SUPAPolicyTerm is in the
ability of its subclasses to define a generic framework for
implementing get and set statements. This is in stark contrast to
previous designs (e.g., [RFC3460] and [6]), which both depended on
defining a broad set of subclasses of PolicyVariable and
PolicyValue. (Note that [4] does not have this generic capability).
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5.10.1. SUPAPolicyTerm Attributes
Currently, SUPAPolicyTerm defines a single attribute, as described
in the following subsection. Constraints on the subclasses of
SUPAPolicyTerm can be applied in two different ways:
1. use SUPAPolicyComponentDecorator attributes to constrain
just that individual subclass, and/or
2. use SUPAHasDecoratedPolicyComponentDetail association class
attributes to constrain the relationship between the concrete
subclass of SUPAPolicyClause and the concrete subclass of
the SUPAPolicyTerm class
5.10.1.1. The Attribute "supaPolTermIsNegated"
This is a mandatory Boolean attribute. If the value of this
attribute is true, then this particular SUPAPolicyTerm subclass
(which represents a term) is negated; otherwise, it is not.
5.10.2. SUPAPolicyTerm Relationships
Currently, no dedicated relationships are defined for the
SUPAPolicyTerm class (as there is in [RFC3460] and [6]) that
aggregate policy terms into any object. This is:
1) to enable the subclasses of SUPAPolicyTerm to be used by
other SUPAPolicyComponentDecorator objects, and
2) because the decorator pattern replaces how such relationships
were used in [RFC3460] and [6].
5.11. The Concrete Class "SUPAPolicyVariable"
This is a mandatory concrete class that defines information that
forms a part of a SUPAPolicyClause. It specifies a concept or
attribute that represents a variable, which should be compared to
a value, as specifed in this SUPAPolicyClause. If it is used in
a SUPAECAPolicyRule, then its value MAY be able to be changed at
any time, including run-time, via use of the decorator pattern.
Note that this is not possible in previous designs ([RFC3460, [4],
and [6]).
The value of a SUPAPolicyVariable is typically compared to the
value of a SUPAPolicyValue using the type of operator defined in
a SUPAPolicyOperator. However, other objects may be used instead
of a SUPAPolicyValue object.
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SUPAPolicyVariables are used to abstract the representation of a
SUPAPolicyRule from its implementation. Some SUPAPolicyVariables
are restricted in the values and/or the data type that they may
be assigned. For example, port numbers cannot be negative, and
they cannot be floating-point numbers. These and other constraints
are defined in two different ways:
1. use SUPAPolicyComponentDecorator attributes to constrain
just that individual subclass, and/or
2. use SUPAHasDecoratedPolicyComponentDetail association class
attributes to constrain the relationship between the concrete
subclass of SUPAPolicyClause and the concrete subclass of
the SUPAPolicyVariable class
Please refer to the examples in section 7, which show how to
restrict the value, data type, range, and other semantics of the
SUPAPolicyVariable when used in a SUPAPolicyClause.
5.11.1. Problems with the RFC3460 Version of PolicyVariable
The following subsections define a brief, and incomplete, set of
problems with the implementation of [RFC3460] (note that [RFC3060
did not define variables, operators, and/or values).
5.11.1.1. Object Bloat
[RFC3460] used two different and complex mechanisms for providing
generic get and set expressions. PolicyVariables were subclassed
into two subclasses, even though they performed the same semantic
function. This causes additional problems:
o PolicyExplicitVariables are for CIM compatibility; note that
the CIM does not contain either PolicyVariables or
PolicyValues ([4])
o PolicyImplicitVariable subclasses do not define attributes;
rather, they are bound to an appropriate subclass of
PolicyValue using an association
Hence, defining a variable is relatively expensive in [RFC3460],
as in general, two objects and an association must be used. The
objects themselves do not define content; rather, their names are
used as a mechanism to identify an object to match. This means
that an entire object must be used (instead of, for example, an
attribute), which is wasteful. It also make it difficult to
adjust constraints at runtime, since the constraint is defined in
a class that is statically defined (and hence, requires
recompilation and possibly redeployment if it is changed).
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5.11.1.2. Object Explosion
The above three problems lead to class explosion (recall that in
[RFC3060], [RFC3460], and [4], associations are implemented as
classes).
In stark contrast to this approach, the approach in this document
keeps the idea of the class hierarchy for backwards compatibility,
but streamlines the implementation. First, the decorator pattern
is an established and very used software pattern (it dates back
to at least 1997). Second, the use of a single association class
(i.e., SUPAHasDecoratedPolicyComponentDetail) performs many more
constraints than is possible in the approaches of [RFC3460] and
[4] in a much more flexible manner, due to its role as a
decorator of other objects. Third, note that there is no way to
enforce the constraint matching in [RFC3460] and [6]; the burden
is on the developer to check and see if the constraints specified
in one class are honored in the other class. Fourth, if these
constraints are not honored, then there is no mechanism specified
to define the statement as incorrectly formed.
5.11.1.3. Specification Ambiguities
There are a number of ambiguities in [RFC2460].
First, [RFC3460] says: "Variables are used for building individual
conditions". While this is true, variables can also be used for
building individual actions. This is reflected in the definition
for SUPAPolicyVariable.
Second, [RFC3460] says: "The variable specifies the property of a
flow or an event that should be matched when evaluating the
condition." While this is true, variables can be used to test many
other things than "just" a flow or an event. This is reflected in
the SUPAPolicyVariable definition.
Third, the [RFC3460] definition requires the use of associations
in order to properly constrain the variable (e.g., define its
data type, the range of its allowed values, etc.). This is both
costly and inefficient.
Fourth, [RFC3460] is tightly bound to the DMTF CIM schema [4].
The CIM is a data model (despite its name), because:
o It uses keys and weak relationships, which are both concepts
from relational algebra and thus, not technology-independent
o It has its own proprietary modeling language
o It contains a number of concepts that are not defined in UML
(including overriding keys for subclasses)
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Fifth, the class hierarchy has two needless classes, called
SUPAImplicitVariable and SUPAExplicitVariable. These classes do
not define any attributes or relationships, and hence, do not
add any semantics to the model.
Finally, in [RFC3460], defining constraints for a variable is
limited to associating the variable with a PolicyValue. This is
both cumbersome (because associations are costly; for example,
they equate to a join in a relational database management system),
and not scalable, because it is prone to proliferating PolicyValue
classes for every constraint (or range of constraints) that is
possible. Therefore, in SUPA, this mechanism is replaced with
using an association to an association class that defines
constraints in a much more general and powerful manner (i.e.,
the SUPAHasDecoratedPolicyComponentDetail class).
5.11.2. SUPAPolicyVariable Attributes
Currently, SUPAPolicyVariable defines three generic attributes,
as described below.
5.11.2.1. The Attribute "supaPolVarContent"
This is a mandatory string attribute that contains the value of
the SUPAPolicyVariable object instance. Its data type is defined
by the supaPolVarType class attribute.
5.11.2.2. The Attribute "supaPolVarType"
This is a mandatory non-negative enumerated integer attribute
that defines the data type of the supaPolVarContent attribute in
this SUPAPolicyVariable object instance. Values include:
0: Undefined
1: String
2: Integer
3: Boolean
4: Floating Point
5: DateTime
6: GUID
7: UUID
8: URI
9: FQDN
A string is a sequence of zero or more characters. An Integer is
a whole number (e.g., it has no fractional part). A Boolean
represents the values TRUE and FALSE. A floating point number may
contain fractional values, as well as an exponent. A DateTime
represents a value that has a date and/or a time component (as in
the Java or Python libraries).
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In general, specific semantics of the above data types are NOT
defined in this document, as there are differences in most when
converted to a data type of a specific data model. However,
constraints can be used to restrict the values that a String,
Integer, Floating Point, or DateTime data type may have; this can
simplify converting to a data model.
5.11.3. SUPAPolicyVariable Relationships
Currently, no relationships are defiend for the SUPAPolicyVariable
class (note that the decorator pattern obviates the need for
relationships such as those in [RFC3460] and [6]).
5.12. The Concrete Class "SUPAPolicyOperator"
This is a mandatory concrete class for modeling different types of
operators that are used in a SUPAPolicyClause.
A SUPAPolicyOperator is a mandatory concrete class that defines
the type of operator to be applied to a SUPAPolicyClause. The
restriction of the type of operator used in a SUPAPolicyClause
restricts the semantics that can be expressed in that
SUPAPolicyClause (e.g., a "shallow" vs. a "deep" equality
comparison; the former compares just the attributes in the
specified objects, while the latter compares the entire tree of
objects (using the specified objects as the base of both trees).
5.12.1. Problems with the RFC3460 Version
Note that this class is NOT present in either RFC[3060] or
[RFC3460]; instead, both hardwire the operator to a "MATCH"
function. Quoting from [RFC3460]:
"A simple condition models an elementary Boolean expression of
the form 'variable MATCHes value". However, the formal
notation of the SimplePolicyCondition, together with its
associations, models only a pair, (<variable>, <value>). The
'MATCH' operator is not directly modeled -- it is implied.
Furthermore, this implied 'MATCH' operator carries overloaded
semantics [sic]."
In stark contrast to this, SUPA defines a SUPAPolicyOperator as a
formal subclass of SUPAPolicyTerm. A single attribute, called
supaPolOpType, carries the operator to be applied to the
SUPAECAPolicyRule. This has the important advantage of enabling
ECA policy rules of varying functionality to be created by a
human or a machine. It also removes the ambiguity created by
[RFC3460].
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5.12.2. SUPAPolicyOperator Attributes
Currently, SUPAPolicyOperator defines a single generic attribute,
as described below.
5.12.2.1. The Attribute "supaPolOpType"
This is a mandatory non-negative enumerated integer that specifies
the various types of operators that are allowed to be used in this
particular SUPAPolicyClause. Values include:
0: Unknown
1: Greater than (shallow)
2: Greater than or equal to (shallow)
3: Less than (shallow)
4: Less than or equal to (shallow)
5: Equal to (shallow)
6: Not equal to (shallow)
7: IN
8: NOT IN
9: SET
10: CLEAR
11: Greater than (deep)
12: Greater than or equal to (deep)
13: Less than (deep)
14: Less than or equal to (deep)
15: Equal to (deep)
16: Not equal to (deep)
17: BETWEEN
Note that 0 is an unacceptable value. Its purpose is to support
dynamically building a SUPAPolicyClause by enabling the
application to set the value of this attribute to a standard
default value if the real value is not yet known.
5.12.3. SUPAPolicyOperator Relationships
Currently, no relationships are defiend for the SUPAPolicyOperator
class (note that the decorator pattern obviates the need for
relationships such as those in [6]).
5.13. The Concrete Class "SUPAPolicyValue"
The SUPAPolicyValue class is a mandatory concrete class for
modeling different types of values and constants that occur in a
SUPAPolicyClause.
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SUPAPolicyValues are used to abstract the representation of a
SUPAPolicyRule from its implementation. Therefore, the design of
SUPAPolicyValues depends on two important factors. First, just as
with SUPAPolicyVariables (see Section 5.11), some types of
SUPAPolicyValues are restricted in the values and/or the data
type that they may be assigned. Second, there is a high likelihood
that specific applications will need to use their own variables
that have specific meaning to a particular application.
In general, there are two ways to apply constraints to an object
instance of a SUPAPolicyValue:
1. use SUPAPolicyComponentDecorator attributes to constrain
just that individual subclass, and/or
2. use SUPAHasDecoratedPolicyComponentDetail association class
attributes to constrain the relationship between the concrete
subclass of SUPAPolicyClause and the concrete subclass of
the SUPAPolicyValue class
5.13.1. Problems with the RFC3460 Version of PolicyValue
The following subsections define a brief, and incomplete, set of
problems with the implementation of [RFC3460] (note that [RFC3060
did not define variables, operators, and/or values).
5.13.1.1. Object Bloat
[RFC3460] defined a set of 7 subclasses; three were specific to
networking (i.e., IPv4 Address, IPv6 Address, MAC Address) and 4
(PolicyStringValue, PolicyBitStringValue, PolicyIntegerValue, and
PolicyBooleanValue) were generic in nature. However, each of these
objects defined a single class attribute. This has the same two
problems as with PolicyVariables (see section 5.11.1.1):
1. Using an entire object to define a single attribute is very
wasteful and expensive
2. It also make it difficult to adjust constraints at runtime,
since the constraint is defined in a class that is statically
defined (and hence, requires recompilation and possibly
redeployment if it is changed).
5.13.1.2. Object Explosion
[RFC3460] definition requires the use of associations
in order to properly constrain the variable (e.g., define its
data type, the range of its allowed values, etc.). This is both
costly and inefficient (recall that in [RFC3060], [RFC3460], and
[4], associations are implemented as classes).
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5.13.1.3. Lack of Constraints
There is no generic facility for defining constraints for a
PolicyValue. Therefore, there is no facility for being able to
change such constraints dynamically at runtime.
5.13.1.4. Tightly Bound to the CIM Schema
[RFC3460] is tightly bound to the DMTF CIM schema [4]. The CIM is
a data model (despite its name), because:
o It uses keys and weak relationships, which are both concepts
from relational algebra and thus, not technology-independent
o It has its own proprietary modeling language
o It contains a number of concepts that are not defined in UML
(including overriding keys for subclasses)
5.13.1.5. Specification Ambiguity
[RFC3460] says: It is used for defining values and constants used
in policy conditions". While this is true, variables can also be
used for building individual actions. This is reflected in the
SUPAPolicyVariable definition.
5.13.1.6. Lack of Symmetry
Most good information models show symmetry between like components.
[RFC3460] has no symmetry in how it defines variables and values.
In contrast, this document recognizes that variables and values
are just terms in a statement; hence, the only difference in the
definition of the SUPAPolicyVariable and SUPAPolicyValue classes
is that the content attribute in the former is a single string,
whereas the content attribute in the latter is a string array.
In particular, the semantics of both variables and values are
defined using the decorator pattern, along with the attributes of
the SUPAPolicyComponentDecorator and the
SUPAHasDecoratedPolicyComponentDetail classes.
5.13.2. SUPAPolicyValue Attributes
Currently, SUPAPolicyValue defines two generic attributes, as
described below.
5.13.2.1. The Attribute "supaPolValContent[0..n]"
This is a mandatory attribute that defines an array of strings.
The array contains the value(s) of this SUPAPolicyValue object
instance. Its data type is defined by the supaPolValType class
attribute.
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5.13.2.2. The Attribute "supaPolValType"
This is a mandatory string attribute that contains the data type
of the SUPAPolicyValue object instance. Its value is defined by
the supaPolValContent class attribute. Values include:
0: Undefined
1: String
2: Integer
3: Boolean
4: Floating Point
5: DateTime
6: GUID
7: UUID
8: URI
9: FQDN
10: NULL
A string is a sequence of zero or more characters. An Integer is
a whole number (e.g., it has no fractional part). A Boolean
represents the values TRUE and FALSE. A floating point number may
contain fractional values, as well as an exponent. A DateTime
represents a value that has a date and/or a time component (as in
the Java or Python libraries). A NULL explicitly models the lack
of a value.
5.13.3. SUPAPolicyValue Relationships
Currently, no relationships are defiend for the SUPAPolicyValue
class (note that the decorator pattern obviates the need for
relationships such as those in [6]).
5.14. The Concrete Class "SUPAVendorDecoratedComponent"
A SUPAVendorDecoratedComponent enables a custom, vendor-specific
object to be defined and used in a SUPAPolicyClause. This
should not be confused with the SUPAEncodedClause class. The
SUPAVendorDecoratedComponent class represents a single, atomic,
that is vendor-specific object that defines a **portion** of a
SUPAPolicyClause, whereas a SUPAEncodedClause, which may or
may not be vendor-specific, represents an **entire**
SUPAPolicyClause. Note that this object is not present in
[RFC3060], [RFC3460], [4], [5], or [6].
5.14.1. SUPAVendorDecoratedComponent Attributes
Currently, SUPAVendorDecoratedComponent defines two generic
attributes, as described below.
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5.14.1.1. The Attribute "supaVendorDecoratedCompContent[0..n]"
This is a mandatory attribute that defines an array of strings.
This array contains the value(s) of the
SUPAVendorDecoratedComponent object instance. Its data type is
defined by the supaVendorDecoratedFormat class attribute.
5.14.1.2. The Attribute "supaVendorDecoratedCompFormat"
This is a mandatory string attribute that defines the format of
the supaVendorDecoratedContent class attribute. Values include:
0: undefined
1: String
2: Integer
3: Boolean
4: Floating Point
5: DateTime
6: GUID
7: UUID
8: URI
9: FQDN
10: NULL
A string is a sequence of zero or more characters. An Integer is
a whole number (e.g., it has no fractional part). A Boolean
represents the values TRUE and FALSE. A floating point number may
contain fractional values, as well as an exponent. A DateTime
represents a value that has a date and/or a time component (as in
the Java or Python libraries). A NULL explicitly models the lack
of a value.
5.14.2. SUPAVendorDecoratedComponent Relationships
Currently, no relationships are defiend for the
SUPAVendorDecoratedComponent class (note that the decorator
pattern obviates the need for relationships such as those in [6]).
5.15. The Concrete Class "SUPAPolicyCollection"
A SUPAPolicyCollection enables a collection (e.g., set, bag, or
other, more complex, collections of elements) to be defined and
used as part of a SUPAPolicyClause.
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5.15.1. Motivation
One of the problems with ECA policy rules is when a set of events
or conditions needs to be tested. For example, if a set of events
is received, the policy system may need to wait for patterns of
events to emerge (e.g., any number of EventA followed by either
one of event B or two of Event C).
Similarly, a set of conditions, testing the value of an attribute,
may need to be performed. Both of these represent behavior
similar to a set of if-then-else or switch statement.
It is typically not desirable for the policy system to represent
each choice in such conditions as its own policy clause (i.e., a
3-tuple), as this creates object explosion and poor performance.
Furthermore, in these cases, it is often required to have a set of
complex logic to be executed, where the logic varies according to
the particular event or condition that was selected. It is much
too complex to represent this using separate objects, especially
when the logic is application- and/or vendor-specific.
However, recall that one of the goals of this document was to
facilitate the machine-driven construction of policies. Therefore,
a solution to this problem is needed.
5.15.2. Solution
Therefore, this document defines the concept of a collection of
entities, called a SUPAPolicyCollection. Conceptually, the items
to be collected (e.g., events or conditions) are aggregated in
one or more SUPAPolicyCollection objects of the appropriate type.
Another optional SUPAPolicyCollection object could be used to
aggregate logic blocks (including SUPAPolicies) to execute.
Once finished, all appropriate SUPAPolicyCollection objects are
sent to an external system for evaluation.
The computation(s) represented by the SUPAPolicyCollection may be
part of a larger SUPAPolicyClause; this is supported, since
SUPAPolicyCollection is a subclass of SUPAPolicyComponentDecorator,
and can be used to decorate a SUPAPolicyClause. Therefore, the
external system is responsible for providing a Boolean TRUE or
FALSE return value, so that the policy system can use that value
to represent the computation of the function(s) performed in the
SUPAPolicyCollection in a Boolean clause.
5.15.3. SUPAPolicyCollection Attributes
Currently, SUPAVendorDecoratedComponent defines two generic
attributes, as described below.
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5.15.3.1. The Attribute "supaPolCollectionContent[0..n]"
This is a mandatory attribute that defines an array of strings.
This array defines the content of this SUPAPolicyCollection
instance.
5.15.3.2. The Attribute "supaPolCollectionDataType"
This is a mandatory non-negative enumerated integer that defines
the data type of the content of this collection instance. Values
include:
0: undefined
1: String
2: Integer
3: Boolean
4: Floating Point
5: DateTime
6: GUID
7: UUID
8: URI
9: FQDN
5.15.3.3. The Attribute "supaPolCollectionFunction"
This is a mandatory non-negative enumerated integer that defines
the function of this collection instance. Values include:
0: undefined
1: event collection
2: condition collection
3: action collection
4: logic collection
5.15.3.4. The Attribute "supaPolCollectionIsOrdered"
This is an optional Boolean attribute. If the value of this
attribute is TRUE, then all elements in this instance of this
SUPAPolicyCollection are ordered.
5.15.3.5. The Attribute "supaPolCollectionType"
This is a mandatory non-negative enumerated integer that defines
the type of collection that this instance is. Values include:
0: undefined
1: set
2: bag (e.g., multi-set)
3: dictionary (e.g., associative array)
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A bag is an unordered collection of elements; it MAY also have
duplicates. A set is an unordered collection of elements that
MUST NOT have duplicates. A dictonary is a table that associates
a key with a value.
Sets have a number of important functions:
o membership: returns TRUE if the element being tested is
in the set, and FALSE otherwise
o subset: returns TRUE if all elements in the first set
are also in the second set
o union: returns all elements from both sets with no
duplicates
o intersection: returns all elements that are in both sets
with no duplicates
o difference: returns all elements in the first set that
are not in the second set
Bags have a number of important functions in addition to the
functions defined for sets (note that while the above set of
functions for a set and a bag are the same, a bag is a different
data type than a set):
o multiplicity: returns the number of occurrences of an
element in the bag
o count: returns the number of all items, including
duplicates
o countDistinct: returns the number of items, where all
duplicates are ignored
A dictionary is an unordered set of key:value pairs, where each
key is unique witin a given dictionary.
5.15.4. SUPAPolicyCollection Relationships
Currently, no relationships are defiend for the
SUPAVendorDecoratedComponent class (note that the decorator
pattern obviates the need for relationships such as those in [6]).
5.16. The Concrete Class "SUPAPolicySource"
This is an optional class that defines the set of managed entities
that authored, or are otherwise responsible for, this
SUPAPolicyClause. Note that a SUPAPolicySource does NOT
evaluate or execute SUPAPolicies. Its primary use is for
auditability and the implementation of deontic and/or alethic logic.
A class diagram is shown in Figure 12.
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A SUPAPolicySource SHOULD be mapped to a role or set of roles
(e.g., using the role-object pattern [11]). This enables
role-based access control to be used to restrict which entities
can author a given policy. Note that Role is a type of
SUPAPolicyMetadata.
5.16.1. SUPAPolicySource Attributes
Currently, no attributes are defined for the SUPAPolicySource
class.
5.16.2. SUPAPolicySource Relationships
This section defines the relationships of the SUPAPolicySource
class.
5.16.2.1. The Aggregation "SUPAHasPolicySource"
This is an optional association that defines the set of
SUPAPolicySource objects that are associated with this particular
SUPAPolicyStructure object. The multiplicity of this relationship
is defined as 0..n on the aggregate (i.e., SUPAPolicyStructure)
side, and 0..n on the part (i.e., SUPAPolicySource) side. This
means that this relationship is optional. The semantics of this
aggregation are implemented using the SUPAHasPolicySourceDetail
association class.
5.16.2.2. The Association Class "SUPAHasPolicySourceDetail"
This is an optional association class that defines the semantics
of the SUPAHasPolicySource aggregation. It is typically used to
constrain the types of SUPAPolicyStructure objects that can
aggregate a particular set of SUPAPolicySource objects.
5.16.2.2.1. The Attribute "SUPAPolSrcIsAuthenticated"
This is an optional Boolean attribute. If the value of this
attribute is true, then this SUPAPolicySource object has been
authenticated by this specific SUPAPolicyStructure object.
5.16.2.2.2. The Attribute "supaPolicySrcIsTrusted"
This is a Boolean attribute. If the value of this attribute is
TRUE, then this particular SUPAPolicySource object has been
verified to be trusted by this specific SUPAPolicyStructure object.
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5.17. The Concrete Class "SUPAPolicyTarget"
A SUPAPolicyTarget is a set of managed entities that a SUPAPolicy
is applied to. This is determined by two conditions.
First, the set of managed entities that are to be affected by the
SUPAPolicy must all agree to play the role of a SUPAPolicyTarget.
In general, a managed entity may or may not be in a state that
enables SUPAPolicies to be applied to it to change its state;
hence, a negotiation process may need to occur to enable the
SUPAPolicyTarget to signal when it is willing to have
SUPAPolicies applied to it.
Second, a SUPAPolicyTarget must be able to either process
(directly or with the aid of a proxy) SUPAPolicies or receive the
results of a processed SUPAPolicy and apply those results to
itself.
If a proposed SUPAPolicyTarget meets both of these conditions, it
SHOULD set its supaPolicyTargetEnabled Boolean attribute to a
value of TRUE.
Figure 12 shows a class diagram of the SUPAPolicyTarget.
A SUPAPolicyTarget SHOULD be mapped to a role (e.g., using the
role-object pattern). This enables role-based access control to
be used to restrict which entities can author a given policy.
Note that Role is a type of SUPAPolicyMetadata.
5.17.1. SUPAPolicyTarget Attributes
Currently, no attributes are defined for the SUPAPolicyTarget
class.
5.17.2. SUPAPolicyTarget Relationships
This section defines the relationships of the SUPAPolicyTarget
class.
5.17.2.1. The Aggregation "SUPAHasPolicyTarget"
This is an optional aggregation that defines the set of
SUPAPolicyTarget objects that can be attached to this particular
SUPAPolicyStructure object. This defines the set of entities that
will be operated on by this particular SUPAPolicyStructure object.
The multiplicity of this relationship is defined as 0..1 on the
aggregate (i.e., SUPAPolicyStructure) side, and 0..n on the part
(i.e., SUPAPolicyTarget) side. The semantics of this aggregation
are implemented using the SUPAIsTargetOfDetail association class.
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5.17.2.2. The Association Class "SUPAHasPolicyTargetDetail"
This is an optional concrete association class that defines the
semantics of the SUPAHasPolicyTarget aggregation. This enables
the attributes and relationships of the SUPAHasPolicyTargetDetail
association class to be used to constrain which SUPAPolicyTarget
objects can be operated on by which SUPAPolicyStructure objects.
5.17.2.2.1. The Attribute "SUPAPolTgtIsAuthenticated"
This is an optional Boolean attribute. If the value of this
attribute is true, then this SUPAPolicyTarget object has been
authenticated by this specific SUPAPolicyStructure object.
5.17.2.2.2. The Attribute "supaPolTgtIsEnabled"
This is an optional Boolean attribute. If its value is TRUE, then
this SUPAPolicyTarget is able to be used as a SUPAPolicyTarget.
This means that it meets two specific criteria:
1. it has agreed to play the role of a SUPAPolicyTarget (i.e.,
it is willing to have SUPAPolicies applied to it, and
2. it is able to either process (directly or with the aid of
a proxy) SUPAPolicies or receive the results of a processed
SUPAPolicy and apply those results to itself.
5.18. The Abstract Class "SUPAPolicyMetadata"
Metadata is information that describes and/or prescribes
characteristics and behavior of another object that is **not**
an inherent, distinguishing characteristic or behavior of that
object (otherwise, it would be an integral part of that object).
For example, a socialSecurityNumber attribute should not be part
of a generic Person class. First, most countries in the world do
not know what a social security number is, much less use them.
Second, a person is not created with a social security number;
rather, a social security number is used to track people for
administering social benefits, though it is also used as a form
of identification.
Continuing the example, a better way to add this capability to a
model would be to have a generic Identification class, then
define a SocialSecurityNumber subclass, populate it as necessary,
and then define a composition between a Person and it (this is a
composition because social security numbers are not reused).
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Since social security numbers are given to US citizens, permanent
residents, and temporary working residents, and because it is
also used to administer benefits, the composition is realized
as an association class to define how it is being used.
An example of descriptive metadata for network elements would be
documentation about best current usage practices (this could also
be in the form of a reference). An example of prescriptive
metadata for network elements would be the definition of a time
period during which specific types of operations are allowable.
This class defines a hierarchy of model elements that are used to
define different types of metadata that can be applied to policy
objects that are subclasses of the SUPAPolicyObject class. This
enables common metadata to be defined as objects and then reused
when the metadata are applicable. One way to control whether
SUPAPolicyMetadata objects are reused is by using the attributes
of the SUPAHasPolicyMetadataDetail association class. This is an
abstract class, and is meant to be subclassed to include more
detailed metadata attributes and relationships, as appropriate to
the needs of the policy management application.
5.18.1. SUPAPolicyMetadata Attributes
This section defines the attributes of the SUPAPolicyMetadata
class. This class is the base class of the metadata hierarchy for
policy objects.
5.18.1.1. The Attribute "supaPolMetadataDescription"
This is an optional string attribute that defines a free-form
textual description of this metadata object.
5.18.1.2. The Attribute "supaPolMetadataIDContent"
This is a mandatory string attribute that represents part of the
object identifier of an instance of this class. It defines the
content of the object identifier. It works with another class
attribute, called supaPolMetadataIDFormat, which defines how to
interpret this attribute. These two attributes form a tuple,
and together enable a machine to understand the syntax and value
of an object identifier for the object instance of this class.
5.18.1.3. The Attribute "supaPolMetadataIDFormat"
This is a mandatory non-zero enumerated integer attribute that
represents part of the object identifier of an instance of this
class. It defines the format of the object identifier. It works
with another class attribute, called supaPolMetadataIDContent,
which defines the content of the object ID.
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These two attributes form a tuple, and together enable a machine
to understand the syntax and value of an object identifier for
the object instance of this class. The supaPolMetadataIDFormat
attribute is mapped to the following values:
0: undefined
1: GUID
2: UUID
3: primary key
4: foreign key
5: URI
6: FQDN
The value 0 may be used to initialize the system, or to signal
that there is a problem with thius particular SUPAPolicyObject.
5.18.1.4. The Attribute "supaPolicyName"
This is an optional string attribute that defines the name of this
SUPAPolicyMetadata object.
5.18.2. SUPAPolicyMetadata Relationships
This is a mandatory aggregation that defines the set of
SUPAPolicyMetadata that are aggregated by this particular
SUPAPolicyObject. The multiplicity of this relationship is defined
as 0..n on the aggregate (SUPAPolicyObject) side, and 0..n on the
part (SUPAPolicyMetadata) side. This means that this relationship
is optional. The semantics of this aggregation are
implemented using the SUPAHasPolicyMetadataDetail
association class.
5.18.3. The Abstract Class "SUPAHasPolicyMetadataDetail"
This is a mandatory abstract association class, and defines the
semantics of the SUPAHasPolicyMetadata aggregation. Its purpose is
to determine which SUPAPolicyMetadata object instances should be
attached to which particular object instances of the
SUPAPolicyObject class. This is done by using the attributes and
relationships of the SUPAPolicyMetadataDetail class to constrain
which SUPAPolicyMetadata objects can be aggregated by which
particular SUPAPolicyObject instances.
5.18.3.1. The Attribute "supaPolMetadataIsApplicable"
This is an optional Boolean attribute. If the value of this
attribute is TRUE, then the SUPAPolicyMetadata object(s) of this
particular SUPAHasPolicyMetadata aggregation SHOULD be aggregated
by this particular SUPAPolicyObject.
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5.18.3.2. The Attribute "supaPolMetadataConstraintEncoding"
This is an optional non-negative enumerated integer that defines
how to interpret each string in the supaPolMetadataConstraint
class attribute. Values include:
0: undefined
1: OCL 2.4
2: OCL 2.x
3: OCL 1.x
4: QVT 1.2 - Relations Language
5: QVT 1.2 - Operational language
6: Alloy
The latest version of OCL is 2.4, but since this is considered by
most the default language for specifying constraints, enumerations
1-3 are dedicated to OCL. QVT defines a set of languages; the two
most powerful and useful are defined by enumerations 4 and 5.
Alloy is a language for describing constraints, and uses a SAT
solver to guarantee correctness.
5.18.3.3. The Attribute "supaPolMetadataPolicyConstraints[0..n]"
This is an optional array of string attributes. Each attribute
specifies a constraint to be applied using the format identified
by the value of the supaPolMetadataPolicyConstraintEncoding class
attribute. This provides a more rigorous and flexible treatment of
constraints than is possible in [RFC3460].
5.19. The Concrete Class "SUPAPolicyConcreteMetadata"
This class will be defined in the next release of this document.
5.20. The Abstract Class "SUPAPolicyMetadataDecorator"
This class will be defined in the next release of this document.
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6. SUPA ECAPolicyRule Information Model
This section defines the classes, attributes, and relationships
of the SUPA ECAPolicyRule Information Model (EPRIM). Unless
otherwise stated, all classes (and attributes) defined in this
section were abstracted from DEN-ng [2], and a version of them are
in the process of being added to [5].
6.1. Overview
Conceptually, the EPRIM is a set of subclasses that specialize the
concepts defined in the GPIM for representing the components of a
Policy that uses ECA semantics. This is shown in Figure 21 (only
new EPRIM subclasses and their GPIM superclasses are shown).
(Class of another model that SUPA is integrating into)
|
+---SUPAPolicyObject (5.2)
|
+---SUPAPolicyStructure (5.3)
| |
| +---SUPAPolicyStructureAtomic (5.4)
| |
| +---SUPAECAPolicyRule (6.4)
| |
| +---SUPAECAPolicyRuleAtomic (6.5)
| |
| +---SUPAECAPolicyRuleComposite (6.6)
|
+---SUPAPolicyComponentStructure (5.6)
|
+---SUPAPolicyClause (5.7)
| |
| +---SUPABooleanClause (6.7)
| |
| +---SUPAECAPolicyRuleAtomic (6.8)
| |
| +---SUPAECAPolicyRuleComposite (6.9)
|
+---SUPAPolicyComponentDecorator (5.9)
|
+---SUPAECAComponent(6.10)
| |
| +---SUPAPolicyEvent (6.11)
| |
| +---SUPAPolicyCondition (6.12)
| |
| +---SUPAPolicyAction (6.13)
Figure 21. The EPRIM Class Hierarchy
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Specifically, the EPRIM specializes the SUPAPolicyStructureAtomic
class to create a SUPAECAPolicyRule (see sections 6.4 - 6.6); it
also specializes two subclasses of the SUPAPolicyComponentStructure
class to create two new sets of policy components. Specifically, a
new subclass of SUPAPolicyClause, called SUPABooleanClause (see
sections 6.7 - 6.9), is defined for constructing Boolean clauses
that are specific to the needs of ECA Policy Rules. In addition, a
new subclass of SUPAPolicyComponentDecorator, called
SUPAECAComponent (see sections 6.10 - 6.13), is defined for
constructing reusable objects that represent Events, Conditions,
and Actions.
Note that the EPRIM only defines new (sub)classes that are a
subclass of SUPAPolicyStructure or SUPAPolicyComponentStructure.
This ensures that the semantics of the GPIM are not changed
while providing new functionality for ECA Policy Rules.
The overall strategy for refining the GPIM is as follows:
o SUPAECAPolicyRule is defined as a subclass of the GPIM
SUPAPolicyStructureAtomic class
o A SUPAECAPolicyRule has event, condition, and action clauses
o Conceptually, this can be viewed as three aggregations
between the SUPAECAPolicyRule and each clause
o Each aggregation uses an instance of a concrete subclass of
SUPAPolicyClause; this can be a SUPABooleanClause
(making it ECA-specific) or a SUPAEncodedClause (making it
generic in nature)
o Either of the above object instances may be decorated with
zero or more concrete subclasses of the
SUPAPolicyComponentDecorator class
o An optional set of GPIM SUPAPolicySource objects can be
defined to represent the authoring of a SUPAECAPolicyRule
o An optional set of GPIM SUPAPolicyTarget objects can be
defined to represent the set of managed entities that will be
affected by this SUPAECAPolicyRule
o An optional set of SUPAPolicyMetadata can be defined for any
of the objects that make up a SUPAECAPolicyRule, including
any of its components
6.2. Constructing a SUPAECAPolicyRule
There are several different ways to construct a SUPAECAPolicyRule;
they differ in which set of components are used to define the
content of the SUPAECAPolicyRule, and whether each component is
decorated or not. The following are some examples of creating a
SUPAECAPolicyRule:
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o Define three types of SUPABooleanClauses, one each for the
event, condition, and action clauses that make up a
SUPAECAPolicyRule
o For one or more of the above clauses, associate an
appropriate set of SUPAPolicyEvent, SUPAPolicyCondition, or
SUPAPolicyAction
objects, and complete the clause using an appropriate
SUPAPolicyOperator and a corresponding SUPAPolicyValue or
SUPAPolicyVariable
o Note that compound Boolean clauses may be formed using
one or more SUPABooleanComposite objects with one or more
SUPABooleanAtomic objects
o Define a SUPAPolicyCollectionComponent, which is used to
aggregate a set of SUPAECAComponents, and complete the clause
using an appropriate SUPAPolicyOperator and a corresponding
SUPAPolicyValue or SUPAPolicyVariable
o Create a new concrete subclass of SUPAPolicyComponentStructure
(i.e., a sibling class of SUPAPolicyComponentDecorator and
SUPAPolicyClause), and use this new subclass in a concrete
subclass of SUPABooleanClause; note that this approach enables
the new concrete subclass of SUPAPolicyComponentStructure to
optionally be decorated as well
use it as part of a SUPAPolicyClause
o Create a new subclass of SUPAPolicyComponentDecorator that
provides ECA-specific functionality, and use that to decorate
a SUPAPolicyClause
o Create a new concrete subclass of subclass of
SUPAECAPolicyRule that provides ECA-specific functionality,
and define all or part of its content by aggregating a set of
SUPAPolicyClauses
6.3. Working With SUPAECAPolicyRules
A SUPAECAPolicyRule is a type of SUPAPolicy. It is a tuple that
MUST have three clauses, defined as follows:
o The event clause defines a Boolean expression that, if
TRUE, triggers the evaluation of its condition clause (if the
event clause is not TRUE, then no further action for this
policy rule takes place).
o The condition clause defines a Boolean expression that, if
TRUE, enables the actions in the action clause to be executed
(if the condition clause is not TRUE, then no further action
for this policy rule takes place).
o The action clause contains a set of actions
Each of the above clauses can be a simple Boolean expression (of
the form {variable operator value}, or a compound Boolean
expression consisting of Boolean combinations of clauses.
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Note that each of the above three clauses MAY have a set of
SUPAPolicyMetadata objects that can constrain, or otherwise
affect, how that clause is treated. For example, a set of
SUPAPolicyMetadata MAY affect whether none, some, or all actions
are executed, and what happens if an action fails.
Each of the three clauses can be constructed from either a
SUPAEncodedClause or a SUPABooleanClause. The advantage of using
SUPAEncodedClauses is simplicity, as the content of the clause is
encoded directly into the attributes of the SUPAEncodedClause. The
advantage of using SUPABooleanClauses is reusability, since each
term in each clause is potentially a reusable object.
Since a SUPABooleanClause is a subclass of a SUPAPolicyClause
(see Section 6.7), it can be decorated by one or more concrete
subclasses of SUPAPolicyComponentDecorator. Therefore, a
SUPAECAPolicyRule can be built entirely from objects defined in
the GPIM and EPRIM, which facilitates the construction of
SUPAPolicies by a machine.
The construction of a SUPAECAPolicyRule is shown in Figure 22, and
is explained in further detail in Section 6.4.
SUPAHasPolicyClause
+------------------+---------------+
| ^ |
| | |
/ \ | |
A | |
A \ / 0..1 | A 1..n \ /
+-------------+-------------+ | +----------+-------+
| SUPAPolicyStructureAtomic | | | SUPAPolicyClause |
+----------+----------------+ | +------------------+
/ \ |
I A |
I +-----------+---------------+
I | SUPAHasPolicyClauseDetail |
I +---------------------------+
C I
+----------+----------+
| SUPAECAPolicyRule |
+---------------------+
Figure 22. SUPAECAPolicyRule Clauses
The SUPAHasPolicyClause aggregation is implemented using the
SUPAHasPolicyClauseDetail association class. These were
described in sections 5.4.2.1 and 5.4.2.2, respectively.
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6.4. The Abstract Class "SUPAECAPolicyRule"
This is a mandatory abstract class, which is a PolicyContainer
that aggregates PolicyEvents, PolicyConditions, PolicyActions into
a type of policy rule known as an Event-Condition-Action (ECA)
policy rule. As previously explained, this has the following
semantics:
IF the event clause evaluates to TRUE
IF the condition clause evaluates to TRUE
THEN execute actions in the action clause
ENDIF
ENDIF
The event clause, condition clause, and action clause collectively
form a three-tuple. Each clause MUST be defined by at least one
SUPAPolicyClause (which MAY be decorated with other elements,
as described in section 5.9.
Each of the three types of clauses is of the form
variable operator value
Each of the three clauses MAY be combined with additional clauses
using any combination of logical AND, OR, and NOT operators; this
forms a "compound" Boolean clause. For example, a valid event
clause could be:
"3 A-events AND ((NOT B-event) OR 2 C-events)"
In either case, the output of all three clauses is either TRUE
or FALSE; this facilitates combining and chaining ECAPolicyRules.
An ECAPolicyRule MAY be optionally augmented with PolicySources
and/or PolicyTargets (see sections 5.16 and 5.17, respectively).
In addition, all objects that make up the SUPAECAPolicyRule MAY
have PolicyMetadata attached to them to further describe and/or
specify behavior.
When defined in an information model, each of the event, condition,
and action clauses MUST be represented as an aggregation between a
SUPAECAPolicyRule (the aggregate) and a set of event, condition, or
action objects (the components). However, a data model MAY map
these definitions to a more efficient form (e.g., by flattening
these three types of object instances, along with their respective
aggregations, into a single object instance).
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The composite pattern [3] is applied to the SUPAECAPolicyRule
class, enabling its (concrete) subclasses to be used as either a
stand-alone policy rule or as a hierarchy of policy rules. This is
shown in Figure 23.
1..n +-------------------+
\| |
+--------------- + SUPAECAPolicyRule |
| /| |
| +--------+----------+
| / \
| SUPAHasECAPolicyRule I
| I
| I
| I
| +----------------+---------+
| I I
/ \ I I
A I I
0..1 \ / I I
+-------+--------+---------+ +-----------+-----------+
|SUPAECAPolicyRuleComposite| |SUPAECAPolicyRuleAtomic|
+--------------------------+ +-----------------------+
Figure 23. The Composite Pattern Applied to a SUPAECAPolicyRule
SUPAECAPolicyRuleComposite and SUPAECAPolicyRuleAtomic both
inherit from SUPAECAPolicyRule. This means that they are both
a type of SUPAECAPolicyRule. Hence, the HasSUPAECAPolicyRule
aggregation enables a particular SUPAECAPolicyRuleComposite
object to aggregate both SUPAECAPolicyRuleComposite as well as
SUPAECAPolicyRuleAtomic objects. In contrast, a
SUPAECAPolicyRuleAtomic can NOT aggregate either a
SUPAECAPolicyRuleComposite or a SUPAECAPolicyRuleAtomic.
SUPAECAPolicyRuleAtomic and SUPAECAPolicyRuleComposite are
defined in sections 6.5 and 6.6, respectively.
Note that the HasSUPAECAPolicyRule aggregation is defined by the
HasSUPAECAPolicyRuleDetail association class; both are defined
in sections 6.6.2 and 6.6.3, respectively.
6.4.1. SUPAECAPolicyRule Attributes
Currently, the SUPAECAPolicyRule defines two attributes, as
described in the following subsections.
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6.4.1.1. The Attribute "supaECAPolicyIsMandatory"
This is an optional Boolean attribute. If the value of this
attribute is true, then this SUPAECAPolicyRule MUST be executed
(i.e., its Event and Condition clauses are irrelevant, and the
Action(s) specified in the Action clause MUST be executed). A
default value of FALSE MAY be assigned.
6.4.1.2. The Attribute "supaECAPolicyPriority"
This is a mandatory non-negative integer attribute that defines
the priority of this particular SUPAECAPolicyRule. A larger value
indicates a higher priority. A default value of 0 MAY be assigned.
6.4.1.3. The Attribute "supaECAPolicyRuleStatus"
This is an optionaL non-negative enumerated integer whose value
defines the current status of this policy rule. Values include:
0: In development, not ready to be deployed
1: Ready to be deployed
2: Deployed but not enabled
3: Deployed and enabled, but not executed
4: Executed without errors
5: Executed with errors
6: Aborted during execution
6.4.2. SUPAECAPolicyRule Relationships
Currently, the SUPAECAPolicyRule does not define any relationships.
6.5. The Concrete Class "SUPAECAPolicyRuleAtomic"
This is a mandatory concrete class. This class is a type of
PolicyContainer, and represents a SUPAECAPolicyRule that can
operate as a single, stand-alone, manageable object. Put another
way, a SUPAECAPolicyRuleAtomic object can NOT be modeled as a set
of hierarchical SUPAECAPolicyRule objects; if this is required,
then a SUPAECAPolicyRuleComposite object should be used instead.
6.5.1. SUPAECAPolicyRuleAtomic Attributes
Currently, the SUPAECAPolicyRuleAtomic class does not define any
attributes.
6.5.2. SUPAECAPolicyRuleAtomic Relationships
Currently, the SUPAECAPolicyRuleAtomic class does not define any
relationships.
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6.6. The Concrete Class "SUPAECAPolicyRuleComposite"
This is a mandatory concrete class. This class is a type of
PolicyContainer, and represents a SUPAECAPolicyRule as a hierarchy
of SUPAPolicy objects, where the hierarchy contains instances of a
SUPAECAPolicyRuleAtomic and/or SUPAECAPolicyRuleComposite objects.
Each of the SUPAPolicy objects, including the outermost
SUPAECAPolicyRuleComposite object, are separately manageable. More
importantly, each SUPAECAPolicyRuleComposite object represents an
aggregated object that is itself manageable.
6.6.1. SUPAECAPolicyRuleComposite Attributes
Currently, the SUPAECAPolicyRuleComposite defines one attribute,
as described in the following subsection.
6.6.1.1. The Attribute "supaECAEvalStrategy"
This is a mandatory, non-zero, integer attribute that enumerates
a set of allowable alternatives that define how the actions in a
SUPAECAPolicyRuleComposite object are evaluated. Values include:
0: undefined
1: execute the first action and then terminate
2: execute only the highest priority action(s)
3: execute all actions regardless of their execution status
4: execute all actions until one or more actions fail
Assume that the actions in a given SUPAECAPolicyRuleComposite
are defined as follows
Action A, priority 0
Action B, priority 10
Action C, priority 5
Action D, priority 5
Action E, priority 2
Then, if the supaECAEvalStrategy attribute value equals:
0: an error is issued
1: only Action A is executed
2: only Actions C and D are executed
3: all actions are executed, regardless of any failures
4: all actions are executed until a failure is detected, and
then execution terminates
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6.6.2. SUPAECAPolicyRuleComposite Relationships
Currently, the SUPAECAPolicyRuleComposite defines a single
aggregation between it and SUPAECAPolicyRule, as described below.
6.6.2.1. The Aggregation "SUPAHasECAPolicyRule"
This is an optional aggregation that implements the composite
pattern. The multiplicity of this aggregation is 0..1 on the
aggregate (SUPAECAPolicyRuleComposite) side and 1..n on the part
(SUPAECAPolicyRule) side. This means that if this aggregation
is defined, then at least one SUPAECAPolicyRule object (which may
be either an instance of a SUPAECAPolicyRuleAtomic or a
SUPAECAPolicyRuleComposite class) must also be instantiated and
aggregated by this particular SUPAECAPolicyRuleComposite object.
The semantics of this aggregation are defined by the
SUPHasECAPolicyRuleDetail association class.
6.6.3. The Association Class "SUPHasECAPolicyRuleDetail"
This is an optional association class, and defines the semantics
of the SUPHasECAPolicyRule aggregation. This enables the
attributes and relationships of the SUPHasECAPolicyRuleDetail
class to be used to constrain which SUPHasECAPolicyRule objects
can be aggregated by this particular SUPAECAPolicyRuleComposite
object instance.
6.6.3.1. The Attribute "supaECAPolicyIsDefault"
This is an optional Boolean attribute. If the value of this
attribute is true, then this SUPAECAPolicyRule is a default
policy, and will be executed if no other SUPAECAPolicyRule
in the SUPAECAPolicyRuleComposite container has been executed.
This is a convenient way for error handling, though care should
be taken to ensure that only one default policy rule is defined
per SUPAECAPolicyRuleComposite container.
6.7. The Abstract Class "SUPABooleanClause"
A SUPABooleanClause specializes a SUPAPolicyClause, and defines
a Boolean statement consisting of a standard structure in the form
of a PolicyVariable, a PolicyOperator, and a PolicyValue. For
example, this enables the following Boolean clause to be defined:
Foo >= Bar AND Baz
where 'Foo' is a PolicyVariable, '>=' is a PolicyOperator, and
'Baz' is a PolicyValue.
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Note that in this approach, the PolicyVariable and PolicyValue
terms are defined as an appropriate subclass of the
SUPAPolicyComponentDecorator class; it is assumed that the
PolicyOperator is an instance of the SUPAPolicyOperator class.
This enables the EPRIM, in conjunction with the GPIM, to be used
as a reusable class library. This encourages interoperability,
since each element of the clause is itself an object defined by
the SUPA object hierarchy.
The addition of a negation in the above statement is provided by
the supaBoolIsNegated class attribute of the SUPABooleanClause
class. Individual terms of a Boolean clause can be negated by
using the supaTermIsNegated Boolean attribute in the
SUPAPolicyTerm class (see section 5.10).
A PolicyStatement is in Conjunctive Normal Form (CNF) if it is a
conjunction (i.e., a sequence of ANDed terms), where each term is
a disjunction (i.e., a sequence of ORed terms). Every statement
that consists of a combination of AND, OR, and NOT operators can
be written in CNF.
A PolicyStatement is in Disjunctive Normal Form (DNF) if it is a
disjunction (i.e., a sequence of ORed terms), where each term is
a conjunction (i.e., a sequence of ANDed terms). Every statement
that consists of a combination of AND, OR, and NOT operators can
be written in DNF.
The construction of more complex clauses, which consist of a set
of simple clauses in conjunctive or disjunctive normal form (as
shown in the above example), is provided by using the composite
pattern [3] to construct two concrete subclasses of the abstract)
SUPABooleanClause class. These are called SUPABooleanClauseAtomic
and SUPABooleanClauseComposite, and are defined in sections 6.8
and 6.9, respectively. This enables instances of either a
SUPABooleanClauseAtomic and/or a SUPABooleanClauseComposite to be
aggregated into a SUPABooleanClauseComposite object.
6.7.1. SUPABooleanClause Attributes
The SUPABooleanClause class currently defines two attributes,
which are defined in the following subsections.
6.7.1.1. The Attribute "supaBoolIsCNF"
This is a mandatory Boolean attribute. If the value of this
attribute is TRUE, then this SUPABooleanClause is in CNF form.
Otherwise, it is in DNF form.
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6.7.1.2. The Attribute "supaBoolIsNegated"
This is a mandatory Boolean attribute. If the value of this
attribute is TRUE, then this (entire) SUPABooleanClause is
negated. Note that the supaPolTermIsNegated class attribute of
the SUPAPolicyTerm class is used to negate a single term.
6.7.2. SUPABooleanClause Relationships
Currently, no relationships are defined for the SUPABooleanClause
class.
6.8. The Concrete Class "SUPABooleanClauseAtomic"
This is a mandatory concrete class that represents a
SUPABooleanClause that can operate as a single, stand-alone,
manageable object. Put another way, a SUPABooleanClauseAtomic
object can NOT be modeled as a set of hierarchical clauses; if
this functionality is required, then a SUPABooleanClauseComposite
object must be used.
6.8.1. SUPABooleanClauseAtomic Attributes
No attributes are currently defined for the
SUPABooleanClauseAtomic class.
6.8.2. SUPABooleanClauseAtomic Relationships
Currently, no relationships are defined for the
SUPABooleanClauseAtomic class.
6.9. The Concrete Class "SUPABooleanClauseComposite"
This is a mandatory concrete class that represents a
SUPABooleanClause that can operate as a hierarchy of PolicyClause
objects, where the hierarchy contains instances of
SUPABooleanClauseAtomic and/or SUPABooleanClauseComposite
objects. Each of the SUPABooleanClauseAtomic and
SUPABooleanClauseComposite objects, including the outermost
SUPABooleanClauseComposite object, are separately manageable.
More importantly, each SUPAECAPolicyRuleComposite object
represents an aggregated object that is itself manageable.
6.9.1. SUPABooleanClauseComposite Attributes
A single attribute is currently defined for the
SUPABooleanClauseComposite class, and is described in the
following subsection.
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6.9.1.1. The Attribute "supaPolStmtBindValue"
This is an optional non-zero integer attribute, and defines the
order in which terms bind to a clause. For example, the Boolean
statement "((A AND B) OR (C AND NOT (D or E))) has the following
binding order: terms A and B have a bind value of 1; term C has a
binding value of 2, and terms D and E have a binding value of 3.
6.9.2. SUPABooleanClauseComposite Relationships
Currently, the SUPABooleanClauseComposite class defined a single
aggregation, which is described in the subsections below.
6.9.2.1. The Aggregation "SUPAHasBooleanClause"
This is a mandatory aggregation that defines the set of
SUPABooleanClause objects that are aggregated by this
SUPABooleanClauseComposite object.
The multiplicity of this relationship is 0..1 on the aggregate
(SUPABooleanClauseComposite) side, and 1..n on the part
(SUPABooleanClause) side. This means that one or more
SUPABooleanClauses are aggregated and used to define this
SUPABooleanClauseComposite object. The 0..1 cardinality on the
SUPABooleanClauseComposite side is necessary to enable
SUPABooleanClauses to exist (e.g., in a PolicyRepository) before
they are used by a SUPABooleanClauseComposite. The semantics of
this aggregation is defined by the SUPAHasBooleanClauseDetail
association class.
6.9.3. The Concrete Class "SUPAHasBooleanClauseDetail"
This is a mandatory association class that defines the semantics
of the SUPAHasBooleanClause aggregation. This enables the
attributes and relationships of the SUPAHasBooleanClauseDetail
class to be used to constrain which SUPABooleanClause objects
can be aggregated by this particular SUPABooleanClauseComposite
object instance
6.9.3.1. SUPAHasBooleanClauseDetail Attributes
The SUPAHasBooleanClauseDetail class currently does not define
any attributes at this time.
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6.10. The Abstract Class "SUPAECAComponent"
This is a mandatory abstract class that defines three concrete
subclasses, one each to represent the concepts of reusable events,
conditions, and actions. They are called SUPAPolicyEvent,
SUPAPolicyCondition, and SUPAPolicyAction, respectively.
6.10.1. SUPAECAComponent Attributes
No attributes are currently defined for this class.
6.10.2. SUPAECAComponent Relationships
No relationships are currently defined for this class.
6.11. The Concrete Class "SUPAPolicyEvent"
This is a mandatory concrete class that represents the concept of
an Event that is applicable to a policy management system. Such
an Event is defined as any important occurrence in time of a
change in the system being managed, and/or in the environment of
the system being managed.
6.11.1. SUPAPolicyEvent Attributes
Currently, five attributes are defined for the SUPAPolicyEvent
class, which are described in the following subsections.
6.11.1.1. The Attribute "supaPolicyEventIsPreProcessed"
This is an optional Boolean attribute. If the value of this
attribute is TRUE, then this SUPAPolicyEvent has been pre-
processed by an external entity, such as an Event Service Bus,
before it was received by the Policy Management System.
6.11.1.2. The Attribute "supaPolicyEventIsSynthetic"
This is an optional Boolean attribute. If the value of this
attribute is TRUE, then this SUPAPolicyEvent has been produced by
the Policy Management System. If the value of this attribute is
FALSE, then this SUPAPolicyEvent has been produced by an entity
in the system being managed.
6.11.1.3. The Attribute "supaPolicyEventTopic[0..n]"
This is a mandatory array of string attributes, and contains the
subject that this PolicyEvent describes.
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6.11.1.4. The Attribute "supaPolicyEventDataType"
This is a mandatory non-zero enumerated integer attribute, and
defines the data type of the supaPolicyEventData attribute. These
two attributes form a tuple, and together enable a machine to
understand the syntax and value of the content of this
SUPAPolicyEvent object. Values include:
0: undefined
1: GUID
2: UUID
3: URI
4: FQDN
5: DateTime
6: String
7: OCL 2.x
8: OCL 1.x
9: QVT 1.2 - Relations Language
10: QVT 1.2 - Operational language
11: Alloy
Enumerations 1-4 are used to provide a reference to an event
object. Enumeration 5 defines the Event as a temporal value.
Enumerations 6-11 are used to express the Event as a string.
6.11.1.5. The Attribute "supaPolicyEventData[1..n]"
This is a mandatory array of string attributes that contain the
content of this SUPAPolicyEvent object (or set of objects).
This version of this document enables either the text describing
the set of events that should be contained in the event clause of
a SUPAPolicyRule or a set of event objects. The former is useful
for describing common conditions, such as "if the time is before
6pm" or "if three events of type A are received and then a single
event of type B or type C is received". The latter is useful for
treating the event as an object, and filtering on the attributes
of the event.
In the former case, the text may be entered as one or more strings.
In the latter case, each string in the array is a reference to an
event object.
This attribute works with another class attribute, called
supaPolicyEventDataType, which defines how to interpret this
attribute. These two attributes form a tuple, and together enable
a machine to understand the syntax and value of the data carried
by the object instance of this class.
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6.11.2. SUPAPolicyEvent Relationships
No relationships are currently defined for this class.
6.12. The Concrete Class "SUPAPolicyCondition"
This is a mandatory concrete class that represents the concept of
an Condition that will determine whether or not the set of Actions
in the SUPAECAPolicyRule to which it belongs are executed or not.
6.12.1. SUPAPolicyCondition Attributes
Currently, two attributes are defined for the SUPAPolicyCondition
class, which are described in the following subsections.
6.12.1.1. The Attribute "supaPolicyConditionDataType"
This is a mandatory non-zero enumerated integer attribute, and
defines the data type of the supaPolicyConditionData attribute.
These two attributes form a tuple, and together enable a machine
to understand the syntax and value of the content of this
SUPAPolicyCondition object. Values include:
0: undefined
1: String
2: OCL 2.x
3: OCL 1.x
4: QVT 1.2 - Relations Language
5: QVT 1.2 - Operational language
6: Alloy
6.12.1.2. The Attribute "supaPolicyConditionData"
This is a mandatory string attribute that contains the content of
this SUPAPolicyCondition object.
This attribute works with another class attribute, called
supaPolicyConditionDataType, which defines how to interpret this
attribute. These two attributes form a tuple, and together enable
a machine to understand the syntax and value of the data carried
by the object instance of this class.
6.12.2. SUPAPolicyEvent Relationships
No relationships are currently defined for this class.
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6.13. The Concrete Class "SUPAPolicyAction"
This is a mandatory concrete class that represents the concept of
an Action, which is a part of a SUPAECAPolicyRule, which may be
executed when both the event and the condition clauses of its
owning SUPAECAPolicyRule evaluate to true. The execution of this
action is determined by the SUPAECAPolicyRule container, and any
applicable SUPAPolicyMetadata objects.
6.13.1. SUPAPolicyAction Attributes
Currently, three attributes are defined for the SUPAPolicyCondition
class, which are described in the following subsections.
6.13.1.1. The Attribute "supaPolicyActionDataType"
This is a mandatory non-zero enumerated integer attribute, and
defines the data type of the supaPolicyActionData attribute.
These two attributes form a tuple, and together enable a machine
to understand the syntax and value of the content of this
SUPAPolicyAction object. Values include:
0: undefined
1: GUID
2: UUID
3: URI
4: FQDN
5: String
6: OCL 2.x
7: OCL 1.x
8: QVT 1.2 - Relations Language
9: QVT 1.2 - Operational language
10: Alloy
Enumerations 1-4 are used to provide a reference to an action
object. Enumerations 5-10 are used to express the action to
perform as a string.
6.13.1.2. The Attribute "supaPolicyActionData[1..n]"
This is a mandatory string attribute that contains the content of
this SUPAPolicyAction object.
This attribute works with another class attribute, called
supaPolicyConditionDataType, which defines how to interpret this
attribute. These two attributes form a tuple, and together enable
a machine to understand the syntax and value of the data carried
by the object instance of this class.
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6.13.1.3. The Attribute "supaPolicyActionResponse"
This is a mandatory non-negative enumerated integer attribute that
defines the execution status of this particular SUPAPolicyAction.
Values include:
0: undefined
1: executed with no errors
2: executed with at least one error
3: failed to execute
6.13.2. SUPAPolicyAction Relationships
No relationships are currently defined for this class.
7. Examples
8. Security Considerations
This will be defined in the next version of this document.
9. IANA Considerations
This document has no actions for IANA.
10. Acknowledgments
This document has benefited from reviews, suggestions, comments
and proposed text provided by the following members, listed in
alphabetical order: Andy Bierman, Bob Natale, Fred Feisullin,
Liu (Will) Shucheng, Marie-Jose Montpetit.
11. References
This section defines normative and informative references for this
document.
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3060] Moore, B., Ellesson, E., Strassner, J., Westerinen,
A., "Policy Core Information Model -- Version 1
Specification", RFC 3060, February 2001
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[RFC3460] Moore, B., ed., "Policy Core Information Model (PCIM)
Extensions, RFC 3460, January 2003
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)",
RFC 6020, October 2010.
[RFC6991] Schoenwaelder, J., "Common YANG Data Types", RFC 6991,
July 2013.
11.2. Informative References
[RFC3198] Westerinen, A., Schnizlein, J., Strassner, J.,
Scherling, M., Quinn, B., Herzog, S., Huynh, A.,
Carlson, M., Perry, J., Waldbusser, S., "Terminology
for Policy-Based Management", RFC 3198, November, 2001
[1] Strassner, J., "Policy-Based Network Management",
Morgan Kaufman, ISBN 978-1558608597, Sep 2003
[2] Strassner, J., ed., "The DEN-ng Information Model",
add stable URI
[3] Riehle, D., "Composite Design Patterns", Proceedings
of the 1997 Conference on Object-Oriented Programming
Systems, Languages and Applications (OOPSLA '97).
ACM Press, 1997, Page 218-228
[4] DMTF, CIM Schema, v2.44,
http://dmtf.org/standards/cim/cim_schema_v2440
[5] Strassner, J., ed., "ZOOM Policy Architecture and
Information Model Snapshot", TR235, part of the
TM Forum ZOOM project, October 26, 2014
[6] TM Forum, "Information Framework (SID), GB922 and
associated Addenda, v14.5,
https://www.tmforum.org/information-framework-sid/
[7] Liskov, B.H., Wing, J.M., "A Behavioral Notion of
subtyping", ACM Transactions on Programming languages
and Systems 16 (6): 1811 - 1841, 1994
[8] Klyus, M., Strassner, J., editors, "SUPA Proposition",
IETF Internet draft, draft-klyus-supa-proposition-01,
July 4015
[9] ISO/IEC 10746-3 (also ITU-T Rec X.903), "Reference
Model Open Distributed Processing Architecture",
April 20, 2010
Strassner, et al. Expires July 4, 2016 [Page 101]
Internet-Draft SUPA Generic Policy Model January 2016
[10] Davy, S., Jennings, B., Strassner, J., "The Policy
Continuum - A Formal Model", Proc. of the 2nd Intl.
IEEE Workshop on Modeling Autonomic Communication
Environments (MACE), Multicon Lecture Notes, No. 6,
Multicon, Berlin, 2007, pages 65-78
[11] Gamma, E., Helm, R., Johnson, R., Vlissides, J.,
"Design Patterns - Elements of Reusable Object-Oriented
Software", Addison-Wesley, 1994, ISBN 0-201-63361-2
[12] Strassner, J., de Souza, J.N., Raymer, D., Samudrala,
S., Davy, S., Barrett, K., "The Design of a Novel
Context-Aware Policy Model to Support Machine-Based
Learning and Reasoning", Journal of Cluster Computing,
Vol 12, Issue 1, pages 17-43, March, 2009
[13] Liskov, B.H., Wing, J.M., "A Behavioral Notion of
subtyping", ACM Transactions on Programming languages
and Systems, 16 (6): 1811 - 1841, 1994
[14] Martin, R.C., "Agile Software Development, Principles,
Patterns, and Practices", Prentice-Hall, 2002,
ISBN: 0-13-597444-5
Authors' Addresses
John Strassner
Huawei Technologies
2330 Central Expressway
Santa Clara, CA 95138 USA
Email: john.sc.strassner@huawei.com
Joel Halpern
Ericsson
P. O. Box 6049
Leesburg, VA 20178
Email: joel.halpern@ericsson.com
Jason Coleman
Cisco Systems
124 Copper Lake Lane
Georgetown Tx 78628
Email: routerjockey@me.com
Appendix A. Mathematical Logic Terminology and Symbology
Appendix B. SUPA Logic Statement Information Model
Appendix C. Brief Analyses of Previous Policy Work
Strassner, et al. Expires July 4, 2016 [Page 102]