Generic Policy Model for Simplified Use of Policy Abstractions (SUPA)
draft-strassner-supa-generic-policy-info-model-00
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draft-strassner-supa-generic-policy-info-model-00
Network Working Group J. Strassner
Internet Draft Huawei Technologies
Intended status: Standard Track
Expires: October 26, 2015 April 26, 2015
Generic Policy Model for
Simplified Use of Policy Abstractions (SUPA)
draft-strassner-supa-generic-policy-info-model-00
Abstract
The Simplified Use of Policy Abstractions (SUPA) addresses the
needs of operators and application developers to represent
multiple types of policy rules. This document defines a common
structure for policy rules that is independent of language,
protocol, and the level of abstraction of the content of the
policy rule. This enables multiple policy rule data models to be
constructed from it.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on October 26, 2015.
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Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction ................................................. 5
2. Conventions used in this document ............................ 5
3. Terminology .................................................. 5
3.1. Acronyms................................................. 5
3.2. Definitions ............................................. 6
3.2.1. Core Terminology .................................. 6
3.2.1.1. Information Model ............................. 6
3.2.1.2. Data Model .................................... 6
3.2.1.3. Container ..................................... 6
3.2.1.4. PolicyContainer ............................... 7
3.2.2. Policy Terminology ................................. 7
3.2.2.1. SUPAPolicy .................................... 7
3.2.2.2. SUPAPolicyStatement ........................... 7
3.2.2.3. SUPAECAPolicyRule ............................. 8
3.2.2.4. SUPAGoalPredicate ............................. 9
3.2.2.5. SUPAMetadata .................................. 9
3.2.2.6. SUPAPolicyTarget .............................. 9
3.2.2.7. SUPAPolicySubject ............................ 10
3.2.3. Modeling Terminology .............................. 10
3.2.3.1. Inheritance .................................. 10
3.2.3.2. Relationship ................................. 10
3.2.3.3. Association .................................. 10
3.2.3.4. Aggregation .................................. 11
3.2.3.5. Composition .................................. 11
3.2.3.6. Association Class ............................ 11
3.2.3.7. Multiplicity ................................. 11
3.2.3.8. Navigability ................................. 11
3.3. Symbology .............................................. 11
4. Policy Abstraction Architecture ............................. 12
4.1. Motivation ............................................. 13
4.2. SUPA Approach .......................................... 13
4.3. Structure of SUPA Policies ............................. 14
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Table of Contents (continued)
4.4. SUPA Generic Policy Information Model Overview ......... 15
4.4.1. Architectural Objectives .......................... 15
4.4.2. Scope of Previous Work ............................ 15
4.4.3. SGPIM Assumptions ................................. 16
5. SGPIM Model ................................................. 17
5.1. Overview ............................................... 17
5.2. The Abstract Class "SUPAPolicy" ........................ 18
5.2.1. SUPAPolicy Attributes ............................. 19
5.2.1.1. The Attribute "supaObjectIDContent" .......... 19
5.2.1.2. The Attribute "supaObjectIDFormat" ........... 19
5.2.1.3. The Attribute "supaPolicyName" ............... 20
5.2.2. SUPAPolicy Relationships .......................... 20
5.2.2.1. The Relationship "HasSUPAPolicies" ........... 20
5.2.2.2. The Association Class "HasSUPAPolicyDetail" .. 20
5.3. The Abstract Class "SUPAPolicyAtomic" .................. 20
5.4. The Abstract Class "SUPAPolicyComposite" ............... 21
5.5. The Abstract Class "SUPAPolicyStatement" ............... 21
5.5.1. SUPAPolicyStatement Attributes .................... 22
5.5.1.1. The Attribute "supaPolicyStmtAdminStatus" .... 22
5.5.1.2. The Attribute "supaPolicyStmtExecStatus" ..... 23
5.5.2. SUPAPolicyStatement Subclasses .................... 24
5.5.2.1. The Concrete Class "SUPAEncodedClause" ....... 24
5.5.2.1.1. The Attribute "supaClauseContent" ....... 24
5.5.2.1.2. The Attribute "supaClauseFormat" ........ 24
5.5.2.1.3. The Attribute "supaClauseResponse" ...... 25
5.5.3. SUPAPolicyStatement Relationships ................. 25
5.5.3.1. The Aggregation "HasSUPAPolicyStatements" .... 25
5.5.3.2. The Association Class
"HasSUPAPolicyStmtDetail" ................... 25
5.6. The Abstract Class "SUPAPolicySubject" ................. 25
5.6.1. SUPAPolicySubject Attributes ...................... 26
5.6.2. SUPAPolicySubject Relationships ....................27
5.6.2.1. The Relationship "HasSUPAPolicySubjects" ......27
5.6.2.2. The Association Class
"HasSUPAPolicySubjDetail" ....................27
5.7. The Abstract Class "SUPAPolicyTarget" .................. 31
5.7.1. SUPAPolicyTarget Attributes ....................... 28
5.7.1.1. The Attribute "supaPolicyTargetEnabled" ...... 28
5.7.2. SUPAPolicyTarget Relationships .................... 28
5.7.2.1. The Relationship "HasSUPAPolicyTargets" ...... 28
5.7.2.2. The Association Class "HasSUPAPolicyTgtDetail" 28
5.8. The Abstract Class "SUPAPolicyMetadata" ................ 28
6. SUPA ECAPolicyRule Information Model ........................ 29
6.1. Overview ............................................... 29
6.2. Constructing a SUPAECAPolicyRule ....................... 29
6.3. Working With SUPAECAPolicyRules ........................ 30
6.4. The Concrete Class "SUPAECAPolicyRule" ................. 31
6.4.1. SUPAECAPolicyRule Attributes ...................... 31
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Table of Contents (continued)
6.4.1.1. The Attribute "supaECAPRDeployStatus"......... 31
6.4.1.2. The Attribute "supaECAPRExecStatus"........... 32
6.4.2. SUPAECAPolicyRule Relationships ................... 32
6.4.2.1. The Relationship "HasSUPAEvents" ............. 32
6.4.2.2. The Relationship "HasSUPAConditions" ......... 32
6.4.2.3. The Relationship "HasSUPAActions" ............ 33
6.5. SUPAPolicyStatement Subclasses ......................... 33
6.5.1. Designing SUPAPolicyStatements Using
SUPABooleanClauses ............................... 33
6.6. The Abstract Class "SUPABooleanClause" ................. 34
6.6.1. SUPABooleanClause Attributes ...................... 35
6.6.1.1. The Attribute "supaBoolIsNegated" ............ 35
6.6.2. SUPABooleanClause Relationships ................... 35
6.6.2.1. The Relationship "HasSUPABooleanClauses" ..... 35
6.7. SUPABooleanClause Subclasses ........................... 35
6.7.1. The Abstract Class "SUPABooleanClauseAtomic" ...... 36
6.7.1.1. The Abstract Class "SUPAPolicyVariable" ...... 36
6.7.1.1.1. Problems with the RFC3460 Version of
PolicyVariable ......................... 37
6.7.1.1.2. The Abstract Class "SUPAPolicyVariable" . 37
6.7.1.2. The Concrete Class "SUPAPolicyOperator" ...... 36
6.7.1.3. The Abstract Class "SUPAPolicyValue" ......... 38
6.7.1.3.1. Problems with the RFC3460 Version of
PolicyValue ............................. 38
6.7.1.3.2. The Abstract Class "SUPAPolicyValue" .... 38
6.7.2. The Abstract Class "SUPABooleanClauseComposite" ... 38
6.7.2.1. SUPABooleanClauseComposite Attributes ........ 38
6.7.2.2. SUPABooleanClauseComposite Relationships ..... 38
7. SUPA Goal Predicate Information Model ....................... 39
7.1. Overview ............................................... 39
7.2. Constructing a SUPAGoalPredicate ....................... 39
7.3. Working With SUPAGoalPredicates ........................ 39
7.4. The Abstract Class "SUPAGoalPredicate" ................. 39
8. Security Considerations .................................... 39
9. IANA Considerations ......................................... 39
10. Acknowledgments ............................................ 39
11. References ................................................. 40
11.1. Normative References .................................. 40
11.2. Informative References ............................... 40
Authors' Addresses ............................................. 41
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1. Introduction
The Shared Unified Policy Automation (SUPA) addresses the needs of
operators and application developers to represent multiple types
of policy rules. This document defines a common structure for
policy rules that is independent of language, protocol, and the
level of abstraction of the content of the policy rule. This
enables multiple policy rule data models to be constructed from it.
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.
3. Terminology
This section defines acronyms, terms, and symbology used in the
rest of this document.
3.1. Acronyms
CLI Command Line Interface
ECA Event-Condition-Action
EPRIM ECA Policy Rule Information Model
FOL First Order Logic
GPIM Goal Predicate Policy Information Model
Netconf Network Configuration protocol
OAM Operational, Administrative, and Management
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
SGPIM SUPA Generic Policy Information Model
SUPA Simplified Use of Policy Abstractions
UML Unified Modeling Language
URI Uniform Resource Identifier
YANG A data definition language for use with Netconf.
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3.2. Definitions
This section defines important terms that are used in this document.
3.2.1. Core Terminology
The following terms define the terms "information model" and
"data model".
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 different than that of [RFC3198]. A data
model is defined in [RFC3198] as: "A mapping of the contents of an
information model into a form that is specific to a particular type
of data store or repository." The SUPA definition is more specific.
For example, it takes into account differences between two
implementations that use the same protocol, implementation
language, and data repository, but which have different data
definition and/or query protocols.
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 different than that of [RFC3198]. A data
model is defined in [RFC3198] as: "A mapping of the contents of an
information model into a form that is specific to a particular type
of data store or repository." The SUPA definition is more specific.
For example, it takes into account differences between two
implementations that use the same protocol, implementation language,
and data repository, but which have different data definition
and/or query protocols.
3.2.1.3. 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.
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3.2.1.4. 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 features enables a PolicyContainer
to define the behavior of how its constituent components will be
accessed, queried, stored, retrieved, and how they operate.
3.2.2. Policy Terminology
The following terms define different policy concepts used in the
SUPA Generic Policy Information Model (SGPIM). Note that the
prefix "SUPA" is used for all classes and relationships defined
in the SGPIM in order to ensure name uniqueness. Similarly, the
prefix "supa" is defined for all SUPA class attributes.
3.2.2.1. SUPAPolicy
A SUPAPolicy is an abstract class that is a type of
PolicyContainer. A SUPAPolicy MUST have one or more
SUPAPolicyStatements that define the content of the Policy.
SUPAPolicy is defined generically as a means to manage 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.
A SUPAPolicy MUST have at least one SUPAPolicyStatement. A
SUPAPolicy MAY be qualified by a set of zero or more
SUPAPolicySubjects, SUPAPolicyTargets, and/or SUPAPolicyMetadata
objects (all of which are defined as abstract classes). When
defined in an information model, the SUPAPolicy class MUST have
separate aggregation relationships with the SUPAPolicySubject,
SUPAPolicyTarget, and SUPAPolicyMetadata classes. When implemented
in a data model, the set of SUPAPolicyStatement, SUPAPolicyTarget,
SUPAPolicySubject, and SUPAPolicyMetadata object instances, SHOULD
all be part of a single PolicyContainer object.
3.2.2.2. SUPAPolicyStatement
A SUPAPolicyStatement is an abstract class that contains an
individual or group of related functions; this set of functions
defines a set of actions to take. Examples of actions include
getting information, stating facts about the system being managed,
writing a change to a configuration of one or more managed objects,
and querying information about a set of managed objects.
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SUPAPolicyStatements are objects in their own right, which
facilitates their reuse. SUPAPolicyStatements can also be combined
in a whole-part (containment) relationship under a SUPAPolicy,
thereby forming a SUPAECAPolicyRule or a SUPAGoalPredicate. When
defined in an information model, a SUPAPolicyStatement MUST be
represented as a separate object that aggregates its constituent
components. However, a data model MAY map this definition to a
more efficient form (e.g., flattening the SUPAPolicyStatement and
its aggregated object instances into a single object instance).
3.2.2.3. SUPAECAPolicyRule
An Event-Condition-Action (ECA) Policy (SUPAECAPolicyRule) is an
abstract class that is made up of at least one SUPAPolicyStatement.
In other words, a SUPAECAPolicyRule is a type of PolicyContainer
whose content is defined by one or more SUPAPolicyStatements.
A SUPAECAPolicyRule is a three-tuple, and MUST contain an event
clause, a condition clause, and an action clause. Each of these
three clauses MUST have at least one term corresponding to the
type of clause that it is; it MAY have more than one. If there
are more than one term, then they MUST be combined using Boolean
AND, OR, and NOT operators. For example, a valid event clause
could be: "three events of type A AND NOT an event of type B".
These three clauses enable the semantics of a SUPAECAPolicyRule
to be clearly differentiated from the semantics of other types of
SUPAPolicies that use SUPAPolicyStatements (and other parts of
the SPGIM), such as SUPAGoalPredicates.
The semantics of a SUPAECAPolicyRule are defined as follows:
o the event clause defines a Boolean statement that, if true,
triggers the evaluation of the condition clause of the
SUPAECAPolicyRule
o the condition clause defines a Boolean statement that, if
true, enables the actions of the SUPAECAPolicyRule to be
executed
o the action clause is an aggregation of actions that may be
executed if the event and condition clauses so dictate; the
behavior of the actions is defined using the SUPAMetadata
that has been aggregated by the SUPAECAPolicyRule
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., flattening these
three types of object instances into a single object instance).
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3.2.2.4. SUPAGoalPredicate
A SUPAGoalPredicate is an abstract class that is made up of at
least one SUPAPolicyStatement. In other words, a SUPAGoalPredicate
is a type of PolicyContainer whose content is defined by one or
more SUPAPolicyStatements.
A SUPAGoalPredicate defines what actions to take, but not how to
execute those actions. It is commonly called declarative, or
intent-based, policy.
If the SUPAGoalPredicate is expressed in first order logic (FOL),
then a SUPAGoalPredicate MUST consist of a head clause, and MAY
also contain a body clause. This enables the semantics of a
SUPAGoalPredicate to be clearly differentiated from the semantics
of other types of SUPAPolicies that use SUPAPolicyStatements (and
other parts of the SPGIM), such as SUPAECAPolicyRules. While in
principle higher order logics can be defined, this document is
limited to defining a SUPAGoalPredicate using just FOL. When
implemented in an information model, both the head and body
clauses MUST be defined as objects (or sets of objects). However,
a data model MAY map these definitions to a more efficient form
(e.g., flattening the head and body objects into a single object).
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) that it is attached to. 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
SUPAPolicyStatement. A SUPAPolicyTarget may use one or more
mechanisms to identify the set of managed objects that it
affects; examples include OIDs and URIs.
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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. SUPAPolicySubject
SUPAPolicySubject is an abstract class that defines a set of
managed objects that authored this SUPAPolicyStatement. This is
required for auditability. A SUPAPolicySubject may use one or more
mechanisms to identify the set of managed objects that authored it;
examples include OIDs and URIs.
When defined in an information model, each instance of the
SUPAPolicySubject class MUST have its own aggregation relationship
with each Policy that uses it. However, a data model MAY map these
definitions to a more efficient form (e.g., flattening the
PolicySubject, Metadata, and Policy object instances into a single
object instance).
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 (SGPIM).
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). A subclass does NOT change the
characteristics or behavior of the superclass that it inherits
from. However, a subclass MAY add new attributes and relationships
that distinguish it from the attributes and relationships defined
by its superclass.
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.
3.2.3.3. Association
An association represents a generic dependency between a first
and a second set of entities.
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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. The entity owning the aggregation is
referred to as the "aggregate", and the entity that is aggregated is
referred to as the "part".
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.
3.2.3.6. 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.
3.3. Symbology
To be Done
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4. Policy Abstraction Architecture
This section describes the motivation for the policy abstractions
that are used in SUPA. In summary, the following abstractions are
provided:
o The SGPIM defines a technology-neutral information model that
can express the concept of Policy.
o This version of this document restricts the expression of
Policy to either an event-condition-action tuple, a FOL
predicate, or a combination of these statements.
o Since these two representations are very different in syntax
and content, the content of a Policy is abstracted from its
representation:
o Both SUPAECAPolicyRules and SUPAGoalPredicates are types
of SUPAPolicies
o Both SUPAECAPolicyRules and SUPAGoalPredicates are
constructed from SUPAPolicyStatements
o The syntax of a SUPAECAPolicyRule, and hence its
representation, is different from that of a
SUPAGoalPredicate
o A SUPAPolicy MAY use SUPAECAPolicyRules and/or
SUPAGoalPredicates
o A SUPAPolicy consists of one or more SUPAPolicyStatements,
one or more SUPAPolicyTargets, an optional
SUPAPolicySubject, and optional SUPAPolicyMetadata
o A SUPAPolicy MUST contain at least one SUPAPolicyStatement;
it MAY contain more than one.
o A SUPAECAPolicyRule defines the set of events and conditions
that are responsible for executing its actions; it MUST have
an event clause, a condition clause, and an action clause.
o A SUPAGoalPredicate expresses facts that it believes to be
true without defining how those facts are computed, and
provides an efficient query mechanism for retrieving facts.
Each SUPAPolicyStatement MUST be expressed as a function-free
Horn clause; there are a number of additional restrictions
that are covered in Section 7.
o SUPAMetadata MAY be defined for any type of
SUPAPolicyStatement (as well as for individual objects that
make up a SUPAPolicyStatement).
o SUPAMetadata MAY be prescriptive and/or descriptive in nature.
o A SUPAPolicyTarget is a set of managed objects that the
actions of the SUPAPolicy are applied to.
o A SUPAPolicySubject is a set of managed objects that authored
the SUPAPolicy.
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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.
Both of these examples are commonly referred to as "policy rules",
but they take very different forms, since they are at very
different levels of abstraction and likely 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
algorithms implemented in a particular device).
Note that these two policy rules could 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.
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. Hence,
the need for a common policy framework.
4.2. SUPA Approach
The purpose of the SUPA Generic Policy Information Model (SGPIM)
is to define a common framework for expressing policies at
different levels of abstraction. SUPA uses the SGPIM as a common
vocabulary for representing concepts that are common to expressing
policy, but which are independent of language, protocol,
repository, and level of abstraction. This enables different
policies at different levels of abstraction to form a continuum,
where more abstract policies can be translated into more concrete
policies, and vice-versa.
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It may be necessary to translate the form of a PolicyRule 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, or the Congress
version of Datalog). 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 understand. A common framework for expressing policies
that is independent of the level of abstraction is required in
order to form such a continuum.
4.3. Structure of SUPA Policies
Figure 1 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.
+-----------------------------------------------+
| SUPA Generic Policy Information Model (SGPIM) |
+-----------------------------------------------+
/ \
|
|
+-------------+------------+
| |
| |
+---------------+-----------+ +-----------+--------------+
| SUPAECAPolicyRule | | SUPAGoalPredicate |
| Information Model (EPRIM) | | Information Model (GPRIM)|
+---------------------------+ +--------------------------+
/ \ / \
| |
| |
+-----------+-----------+ +-----------+------------+
| ECAPolicyRule | | GoalPredicate |
| Data Model | | Data Model |
+-----------------------+ +------------------------+
Figure 1: Overview of SUPA Policy Rule Abstractions
Conceptually, the SGPIM 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 SUPAGoalPredicates
(see Section 7). In principle, other types of SUPAPolicies could
be defined, but the current charter is restricted to using these
two types of SUPAPolicies as exemplars.
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The SGPIM defines a SUPAPolicy object as a PolicyContainer that
specifies the structure, content, and metadata of a collection of
policies. The content of a SUPAPolicy is made up of one or more
SUPAPolicyStatements. A SUPAPolicyStatement may, in this release
of SUPA, take one of two forms: SUPAECAPolicyRules (see
Section 6) and SUPAGoalPredicates (see Section 7).
4.4. SUPA Generic Policy Information Model Overview
This section describes the overall design of the SGPIM.
4.4.1. Architectural Objectives
The purpose of the SGPIM is to define the common characteristics
and behavior of Policy independent of how Policy is written.
Specifically, the SGPIM generalizes the concept of Policy to
enable different forms of Policy to be defined that refine its
definition. The implementation of Policy by SGPIM is called SUPA
Policy. For this document, two exemplar forms of SUPAPolicy are
defined: SUPAECAPolicyRules and SUPAGoalPredicates.
4.4.2. Scope of the Previous Work
To be done. Section will include:
o Description of, and problems with, [RFC3060]
o Description of, and problems with, [RFC3460]
o Should this section also talk about CIM or SID? I personally
think that this should be in the gap analysis...
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4.4.3. SGPIM Assumptions
SUPA DOES NOT assume that it is the "root class of everything".
Rather, the design of this information model assumes that the SUPA
classes are inserted into another model at a given point in the
other model.
However, most models do not have a capability to integrate
different namespaces. 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. In this way, different naming schemes,
such as those depending on URIs, FQDNs, primary key - foreign key
relationships, and UUIDs can all be accommodated. This is shown in
Figure 2:
+------------------------------------------+
| Root Class of an Existing Model |
+------------------------------------------+
/ \
|
|
+-----------------+--------------+
| |
| |
+-----------+-----------+ +-----------+------------+
| A Subclass of the | | A Subclass of the |
| Existing Model | | Existing Model |
+-----------------------+ +------------------------+
/ \
|
|
...
|
|
+-----------+------------+
| SUPA Class Hierarchy |
| (SGPIM plus EPRIM |
| and/or GPRIM) |
+------------------------+
Figure 2: Integrating SUPA into an Existing Model
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5. SGPIM Model
This section defines the classes and relationships of the SGPIM.
5.1. Overview
The overall class definition is shown in Figure 3. 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 3, indentation represents subclassing.
(Class of another model that SUPA is integrating into)
|
+---SUPAPolicy (see Section 5.2)
| |
| +---SUPAPolicyAtomic (see Section 5.3)
| |
| +---SUPAPolicyComposite (see Section 5.4)
| |
| +---SUPAPolicyStatement (see Section 5.5)
| |
| +---SUPAPolicySubject (see Section 5.6)
| |
| +---SUPAPolicyTarget (see Section 5.7)
| |
| +---SUPAPolicyMetadata (see Section 5.8)
|
...
Figure 3: Integrating SUPA into an Existing Model
The following subsections define the classes of the SGPIM. If a class has attributes, those attributes are also defined. Relationships are defined according to the class that is the "owner", or primary actor, participating in the relationship.
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5.2. The Abstract Class "SUPAPolicy"
This is a mandatory abstract class. This class is the root of the
SUPA class hierarchy. It defines the common attributes and
relationships that all SUPA subclasses inherit.
Figure 4 shows the SUPAPolicy class, and two of its subclasses
(SUPAPolicyAtomic and SUPAPolicyComposite). This is an
implementation of the composite pattern [3], which enables a
SUPAPolicy to be made up of a stand-alone object (an instance of a
SUPAPolicyAtomic class) or a hierarchy of objects (i.e., instances
of one or more SUPAPolicyAtomic and SUPAPolicyComposite classes).
The use of this software pattern enables SUPA Policies to be
designed as individual objects and/or hierarchies of objects.
+-------------------------------+
| Parent Class of another Model |
+-------------------------------+
/ \
+---------------------+ |
| HasSUPAPolicyDetail | |
+-----+---------------+ |
| |
| 1..n +---------------+----------------+
| \| |
+----+--------| SUPAPolicy |
| /| |
| +--------------------------------+
| / \
| HasSUPAPolicies |
| |
| +-----------+----------+
| | |
| | |
| 0..1 +----------+----------+ +---------+--------+
| / \| | | |
+--- A | SUPAPolicyComposite | | SUPAPolicyAtomic |
\ /| | | |
+---------------------+ +------------------+
Figure 4: The SUPAPolicy Class Hierarchy
Note that a SUPAPolicy is a PolicyContainer object. A
SUPAPolicyAtomic as well as a SUPAPolicyComposite are also
PolicyContainer objects.
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In figure 4:
o Both SUPAPolicyComposite and SUPAPolicyAtomic inherit from
SUPAPolicy
o The diamond with an enclosed "A" represents an aggregation
(see Section 3.2.3.4)
o The HasSUPAPolicies aggregation is implemented as an
association class (see Section 3.2.3.6)
o The multiplicity of the HasSUPAPolicies aggregation is
0..1 - 1..n (zero or one SUPAPolicyComposite object instances
can aggregate one or more SUPAPolicy object instances, see
Section 3.2.3.7)
o The arrow pointing at SUPAPolicy restricts the navigability
of this aggregation (see Section 3.2.3.8)
5.2.1. SUPAPolicy Attributes
This section defines the attributes of the SUPAPolicy class. These
attributes are inherited by all subclasses of the SUPAPolicy class.
5.2.1.1. The Attribute "supaObjectIDContent"
This is a mandatory attribute that represents part of the object
identifier of an instance of this class. It is a string attribute,
and defines the content of the object identifier. It works with
another class attribute, called supaObjectIDFormat, 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].
5.2.1.2. The Attribute "supaObjectIDFormat"
This is a mandatory attribute that represents part of the object
identifier of an instance of this class. It is a string attribute,
and defines the format of the object identifier. It works with
another class attribute, called supaObjectIDContent, 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.
This is based on the DEN-ng class design [2].
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5.2.1.3. 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.
5.2.2. SUPAPolicy Relationships
This section defines the relationships of the SUPAPolicy class.
5.2.2.1. The Relationship "HasSUPAPolicies"
This is a mandatory aggregation that defines the set of
SUPAPolicies that are contained in the instance of this
particular SUPAPolicyComposite object. The multiplicity of this
relationship is defined as 0..1 on the aggregate
(SUPAPolicyComposite) side, and 1..n on the part (SUPAPolicy) side.
This means that this relationship is optional, but if it is
instantiated, then one or more SUPAPolicy objects are contained in
this particular SUPAPolicyComposite object. The semantics of this
aggregation are implemented using the HasSUPAPolicyDetail
association class.
5.2.2.2. The Association Class "HasSUPAPolicyDetail"
This is a mandatory concrete association class that defines the
semantics of the HasSUPAPolicies aggregation. This enables the
attributes and relationships of the HasSUPAPolicyDetail class to
be used to constrain which SUPAPolicy objects can be aggregated
by this particular SUPAPolicyComposite object instance.
Attributes will be added to this class at a later time.
5.3. The Abstract Class "SUPAPolicyAtomic"
This is a mandatory abstract class. This class is a type of
PolicyContainer.
A SUPAPolicyAtomic class represents a SUPA Policy that can operate
as a single, stand-alone, manageable object. Put another way, a
SUPAPolicyAtomic object can NOT be modeled as a set of hierarchical
SUPAPolicy objects; if this functionality is required, then a
SUPAPolicyComposite object must be used.
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No attributes are currently defined for the SUPAPolicyAtomic class.
It serves as a superclass for the different types of SUPA Policies
that are defined. In this release, both a SUPAECAPolicyRule (see
Section 6) as well as a SUPAGoalPredicate (see Section 7) are
defined as subclasses of the SUPAPolicyAtomic class.
5.4. The Abstract Class "SUPAPolicyComposite"
This is a mandatory abstract class. This class is a type of
PolicyContainer.
A SUPAPolicyComposite class represents a SUPA Policy as a
hierarchy of Policy objects, where the hierarchy contains
instances of a SUPAPolicyAtomic and/or SUPAPolicyComposite
object. Each of the SUPA Policy objects, including the outermost
SUPAPolicyComposite object, are separately manageable.
No attributes are currently defined for the SUPAPolicyAtomic class.
It is used to create hierarchical SUPA Policies.
5.5. The Abstract Class "SUPAPolicyStatement"
This is a mandatory abstract class that separates the
representation of a SUPAPolicy from its implementation. Its
subclasses enable the developer to define a SUPAPolicy as either a
completely reusable set of SUPAPolicy objects or as an efficient
encoding made up of attributes.
Both SUPAECAPolicyRules (see Section 6) and SUPAGoalPredicates
(see section 7) MAY use a SUPAEncodedClause (see Section 5.5.1);
the former MAY also use a SUPABooleanClause (see Section 6.4),
while the latter MAY also use a SUPAFOLClause (see Section 7.4).
A class diagram showing SUPAPolicyStatement is shown in Figure 5.
Note that in this figure:
o SUPAPolicyStatement, SUPAPolicyAtomic, and
SUPAPolicyComposite are subclasses of SUPAPolicy
o A SUPAEncodedClause is a subclass of SUPAPolicyStatement,
and may be used by either a SUPAECAPolicyRule or a
SUPAGoalPredicate
o Both the HasSUPAPolicyStatements and the HasSUPAPolicies
aggregations are implemented as association classes
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+-------------------------+ +---------------------+
| HasSUPAPolicyStmtDetail | | HasSUPAPolicyDetail |
+-----+-------------------+ +----------+----------+
| |
| 1 +-----------------+ |
| / \| |/ |
+-------+-------- A | SUPAPolicy |--------+-----------+
| \ /| |\ |
| +-----------------+ 1..n |
| / \ |
| HasSUPAPolicyStatements | HasSUPAPolicies |
| | |
| +------+------+--------+ |
| | | | |
| 1..n +----------+----------+ | | |
| \| | | | |
+---------| SUPAPolicyStatement | | | |
/| | | | |
+---------------------+ | | |
/ \ | | |
| +-----------+------+ | |
| | SUPAPolicyAtomic | | |
| +------------------+ | |
| | |
+-----------+-------+ +--------------+------+ |
| SUPAEncodedClause | | |/ \ |
+-------------------+ | SUPAPolicyComposite | A ----+
| |\ /
+---------------------+ 0..1
Figure 5: SUPAPolicyStatements and SUPAPolicy Classes
5.5.1. SUPAPolicyStatement Attributes
This section defines the attributes of the SUPAPolicyStatement
class. These attributes are inherited by all subclasses of the
SUPAPolicyStatement class.
5.5.1.1. The Attribute "supaPolicyStmtAdminStatus"
This is an optional attribute, which is an enumerated non-negative
integer. It defines the current administrative status of this
SUPAPolicyStatement.
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This attribute can be used to place this particular
SUPAPolicyStatement into a specific administrative state, such as
enabled, disabled, or in test. Note that since a SUPAPolicy (e.g.,
a SUPAECAPolicyRule or a SUPAGoalPredicate) is made up of
SUPAPolicyStatements, 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 SUPAPolicyStatement
from being used. Values 1 and 2 mean that this SUPAPolicyStatement
is administratively enabled or disabled, respectively. A value of
4 means that this SUPAPolicyStatement is in a special test mode.
5.5.1.2. The Attribute "supaPolicyStmtExecStatus"
This is an optional attribute, which is an enumerated non-negative
integer. It defines whether this SUPAPolicyStatement is currently
in use and, if so, what its status is.
This attribute can be used to place this particular
SUPAPolicyStatement into a specific execution state, such as
enabled, disabled, or in test. Note that since a SUPAPolicy (e.g.,
a SUPAECAPolicyRule or a SUPAGoalPredicate) is made up of
SUPAPolicyStatements, this enables all or part of a SUPAPolicy to
be administratively controlled. Values include:
0: Unknown (an error state)
1: Working (i.e., in use and no errors reported)
2: Not Working (i.e., in use, but errors have been reported)
3: In Test (i.e., no operational traffic can be passed)
4: Available (i.e., could be used, but currently isn't)
5: Not Available (i.e., not available for use)
Value 0 denotes an error that prevents this SUPAPolicyStatement
from being used. Values 1-3 mean that this SUPAPolicyStatement is
in use; in addition, this SUPAPolicyStatement is working
correctly, not working correctly, or in a special test state,
respectively. Values 4-5 mean that this SUPAPolicyStatement is
not currently in use; a value of 4 means that it is available and
could be used, while a value of 5 means that it is unavailable.
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5.5.2. SUPAPolicyStatement Subclasses
As stated before, the primary purpose of SUPAPolicyStatement is to
define a common type of Policy statement that can be used to
represent policy content regardless of the type of SUPAPolicy that
is being used (e.g., it is independent of the requirements of a
SUPAECAPolicyRule or a SUPAGoalPredicate). The SGPIM defines one
common subclass of SUPAPolicyStatement, called a SUPAEncodedClause,
that can be used by both SUPAECAPolicyRules as well as
SUPAGoalPredicates. Clauses dedicated to the specific use of a
SUPAECAPolicyRule and a SUPAGoalPredicate are defined in
Sections 6 and 7, respectively.
5.5.2.1. The Concrete Class "SUPAEncodedClause"
This is a mandatory concrete class that specializes (i.e., is a
subclass of) a SUPAPolicyStatement. It defines a generalized
extension mechanism for representing SUPAPolicyStatements that
have not been modeled with other SUPAPolicy objects. Rather, the
Policy Clause is directly encoded into the attributes of the
SUPAEncodedClause. Note that other subclasses of
SUPAPolicyStatement use SUPAPolicy objects to define their content.
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.
5.5.2.1.1. 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.
This is based on the DEN-ng class design [2].
5.5.2.1.2. 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. This is based on the DEN-ng class
design [2].
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5.5.2.1.3. 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 SUPAPolicyStatement that provide a status as to
their correctness and/or evaluation state.
5.5.3. SUPAPolicyStatement Relationships
This section defines the relationships of SUPAPolicyStatement.
5.5.3.1. The Aggregation "HasSUPAPolicyStatements"
This is a mandatory aggregation that defines the set of
SUPAPolicyStatements that are contained in the instance of this
particular SUPAPolicy object. This defines a SUPAPolicy object as
being made up of at least one SUPAPolicyStatement. The multiplicity
of this relationship is defined as 1 on the aggregate (SUPAPolicy)
side, and 1..n on the part (SUPAPolicyStatement) side. This means
that this relationship is mandatory, and each SUPAPolicy object is
made up of at least one SUPAPolicyStatement object. The semantics
of this aggregation are implemented using the
HasSUPAPolicyStmtDetail association class.
5.5.3.2. The Association Class "HasSUPAPolicyStmtDetail"
This is a mandatory concrete association class that defines the
semantics of the HasSUPAPolicyStatements aggregation. This enables
the attributes and relationships of the HasSUPAPolicyStmtDetail
class to be used to constrain which SUPAPolicyStatement objects
can be aggregated by this particular SUPAPolicy object instance.
Attributes will be added to this class at a later time.
5.6. The Abstract Class "SUPAPolicySubject"
This is an optional class that defines the set of managed entities
that authored, or are otherwise responsible for, this
SUPAPolicyStatement. Note that a SUPAPolicySubject does NOT
evaluate or execute SUPAPolicies. Its primary use is for
auditability. A SUPAPolicySubject SHOULD be mapped to a role
(e.g., using the role-object pattern, as DEN-ng does). A class
diagram is shown in Figure 6.
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+------------------------+
| HasSUPAPolicyTgtDetail |
+-----------+------------+
|
| 0..1 +------------+
| / \| |
+------------+-------------- A | |
| HasSUPAPolicyTargets \ /| |
| | SUPAPolicy |
| 0..1 | |
| HasSUPAPolicySubjects / \| |
| +------------+------------ A | |
| | | \ /| |
| | | +------------+
| | | / \
| | +----------+--------------+ |
| | | HasSUPAPolicySubjDetail | |
| | +-------------------------+ |
| | |
| | +--------------------+----+--------------+
| | | | |
| | | | |
| | 0..n +-------+---------+ 0..n +--------+-------+ (other
| | \| | \| | SUPAPolicy
| +------|SUPAPolicySubject| +---|SUPAPolicyTarget| subclasses)
| /| | | /| |
| +-----------------+ | +----------------+
| |
+-----------------------------+
Figure 6. SUPAPolicySubject and SUPAPolicyTarget
In Figure 6:
o SUPAPolicySubject and SUPAPolicyTarget are both subclasses
of SUPAPolicy
o Both the HasSUPAPolicyTargets amd the HasSUPAPolicySubjects
aggregations are implemented as association classes
o The multiplicity of both of the above aggregations are 0..1
on the aggregate (SUPAPolicy) side and 0..n on the target
(i.e., SUPAPolicySubject and SUPAPolicyTarget, respectively)
side. This means that both aggregations are optional. If
either is instantiated, then a SUPAPolicy MAY contain zero
or more SUPAPolicySubject object instances and MAY contain
zero or more SUPAPolicyTarget object instances.
5.6.1. SUPAPolicySubject Attributes
Attributes will be added to this class at a later time.
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5.6.2. SUPAPolicySubject Relationships
This section defines the relationships of the SUPAPolicySubject
class.
5.6.2.1. The Relationship "HasSUPAPolicySubjects"
This is an optional aggregation that defines the set of
SUPAPolicySubjects that are contained in the instance of this
particular SUPAPolicy object. This defines the set of entities
that authored this particular SUPAPolicy object. The multiplicity
of this relationship is defined as 0..1 on the aggregate
(SUPAPolicy) side, and 0..n on the part (SUPAPolicySubject) side.
This means that this relationship is optional, but if it is
implemented, then this particular SUPAPolicy object was authored
by this set of SUPAPolicySubjects. The semantics of this aggregation
are implemented using the HasSUPAPolicySubjDetail association class.
5.6.2.2. The Association Class "HasSUPAPolicySubjDetail"
This is an optional concrete association class that defines the
semantics of the HasSUPAPolicySubjects aggregation. This enables
the attributes and relationships of the HasSUPAPolicySubjDetail
class to be used to constrain which SUPAPolicySubject objects can
be used to author this particular SUPAPolicy object instance.
Attributes will be added to this class at a later time.
5.7. The Abstract Class "SUPAPolicyTarget"
A PolicyTarget 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 between the
SUPAPolicySubject and the SUPAPolicyTarget, wherein the
SUPAPolicyTarget consents to have SUPAPolicies applied to it.
Second, a SUPAPolicyTarget must be able to either process (either
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.
A SUPAPolicySubject SHOULD be mapped to a role (e.g., using the
role-object pattern). Figure 6 shows a class diagram of the
SUPAPolicyTarget.
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5.7.1. SUPAPolicyTarget Attributes
The following subsections define the attributes of a
SUPAPolicyTarget.
5.7.1.1. The Attribute "supaPolicyTargetEnabled"
This is an optional Boolean attribute. If its value is TRUE, then
this indicates that this SUPAPolicyTarget is currently able to
have SUPAPolicies applied to it. Otherwise, this SUPAPolicyTarget
is not able to have SUPAPolicies applied to it.
5.7.2. SUPAPolicyTarget Relationships
This section defines the relationships of the SUPAPolicyTarget
class.
5.7.2.1. The Relationship "HasSUPAPolicyTargets"
This is an optional aggregation that defines the set of
SUPAPolicyTargets that are contained in the instance of this
particular SUPAPolicy object. This defines the set of entities that
will be operated on by this particular SUPAPolicy object. The
multiplicity of this relationship is defined as 0..1 on the
aggregate (SUPAPolicy) side, and 0..n on the part
(SUPAPolicyTarget) side. This means that this relationship is
optional, but if it is implemented, then this particular SUPAPolicy
object will operate on this set of SUPAPolicyTargets. The semantics
of this aggregation are implemented using the
HasSUPAPolicyTgtDetail association class.
5.7.2.2. The Association Class "HasSUPAPolicyTgtDetail"
This is an optional concrete association class that defines the
semantics of the HasSUPAPolicyTargets aggregation. This enables
the attributes and relationships of the HasSUPAPolicyTgtDetail
class to be used to constrain which SUPAPolicyTarget objects can
be operated on by this particular SUPAPolicy object instance.
Attributes will be added to this class at a later time.
5.8. The Abstract Class "SUPAPolicyMetadata"
This will be defined in the next version 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).
6.1. Overview
Conceptually, the EPRIM is a set of subclasses that specialize the
concepts defined in the SGPIM for representing the components of a
Policy that uses ECA semantics. Specifically, the EPRIM specializes
the SUPAPolicyAtomic class to create a SUPAECAPolicyRule; it also
specializes a SUPAPolicyStatement to create a SUPAECAComponent. The
SUPAECAPolicyRule uses the rest of the SGPIM infrastructure to
define a complete Policy model according to ECA semantics.
Specifically:
o Event, condition, and action clauses are subclasses of
SUPAPolicyStatement
o An optional set of SUPAPolicySubjects can be defined to
represent the authoring of a SUPAECAPolicyRule
o An optional set of SUPAPolicyTargets 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
6.2. Constructing a SUPAECAPolicyRule
A SUPAECAPolicyRule is constructed as follows:
o Define three types of SUPABooleanClauses (see Section 6.4),
one each for the event, condition, and action clauses that
make up a SUPAECAPolicyRule (see Section 6.3)
o Define a set of SUPAEvent objects (see Section 6.5.2), and
associate them with the SUPABooleanClause that represents the
event clause of the SUPAECAPolicyRule
o Define a set of SUPACondition objects (see Section 6.5.3),
and associate them with the SUPABooleanClause that represents
the condition clause of the SUPAECAPolicyRule
o Define a set of SUPAAction objects (see Section 6.5.4), and
associate them with the SUPABooleanClause that represents the
action clause of the SUPAECAPolicyRule
o Define a SUPAECAPolicyRule, which is a subclass of the SGPIM
SUPAPolicyAtomic class (see Section 5.3)
o Aggregate the three SUPABooleanClauses into the
SUPAECAPolicyRule
o Optionally, define a set of SUPAPolicySubjects and
SUPAPolicyTargets, and aggregate them into the
SUPAECAPolicyRule
o Optionally, define SUPAPolicyMetadata for any of the above
objects, and aggregate them to the SUPAPolicy objects that
the SUPAPolicyMetadata applies to
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6.3. Working With SUPAECAPolicyRules
A SUPAECAPolicyRule is a type of SUPAPolicy. It is a tuple that has
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 is a set of actions, whose
execution MAY be controlled by the SUPAMmetadata of the
policy rule.
Each of the three clauses is constructed from one or more
SUPABooleanClauses. Since a SUPABooleanClause is a subclass of
SUPAPolicyStatement (see Section 5.5), and a SUPABooleanClause can
aggregate SUPAEncodedClauses (see Sections 5.5.2 and 6.3.2.2), a
SUPAECAPolicyRule is built entirely from components defined in the
SGPIM. As will be shown in Section 7.3, this is also true for
SUPAGoalPredicates. The construction of a SUPAECAPolicyRule is
shown in Figure 7, and is explained in Section 6.4.
+----------------------+ +---------------------+
| SUPAPolicyAtomic | | SUPAPolicyStatement |
+----------------------+ +---------------------+
/ \ / \
| |
| |
+------------+------------+ +------------+------------+
| SUPAECAPolicyRule | | SUPABooleanClause |
+-------------------------+ +-------------------------+
0..1/ \ 0..1/ \ 0..1/ \ 1..n/ \ 1..n/ \ 1..n/ \
\ / \ / \ / | | |
| | | | | |
| | | HasSUPAEvents | | |
| | +------------------+ | |
| | HasSUPAConditions | |
| +----------------------------------+ |
| HasSUPAActions |
+--------------------------------------------------+
Figure 7. SUPAECAPolicyRule Clauses
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6.4. The Concrete Class "SUPAECAPolicyRule"
This is a concrete mandatory class. In keeping with the original
DEN-ng model [1], this class is a PolicyContainer that contains
PolicyEvents, PolicyConditions, PolicyActions, and optionally,
PolicyMetadata. As such, it doesn't have an inherent relationship
with PolicySubject or PolicyTarget; these all represent the
specific semantics for a particular SUPAECAPolicyRule. Hence,
these semantics are defined in an instance of the
SUPAPolicyComposite class if they are required.
The semantics of a SUPAECAPolicyRule may be conceptualized as
follows:
ON RECEIPT OF <policy-event-clause>
IF <policy-condition-clause> EVALUATES TO TRUE
THEN EXECUTE <policy-action-clause>
END
END
In the above, a policy-event-clause, policy-condition-clause, and
a policy-action-clause are each instances of a SUPABooleanClause
(see Section 6.4).
6.4.1. SUPAECAPolicyRule Attributes
Currently, the SUPAECAPolicyRule defines two attributes, as
described in the following subsections.
6.4.1.1. The Attribute "supaECAPRDeployStatus"
This is an optional attribute, which is an enumerated,
non-negative integer. It defines the current deployment status of
this SUPAECAPolicyRule. 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
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6.4.1.2. The Attribute "supaECAPRExecStatus"
This is an optional attribute, which is an enumerated,
non-negative integer that defines the current execution status of
this SUPAECAPolicyRule. 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: executed and SUCEEDED (test mode)
5: executed and FAILED (test mode)
6: currently executing (test mode)
6.4.2. SUPAECAPolicyRule Relationships
Currently, the SUPAECAPolicyRule defines three relationships, as
described in the following subsections.
6.4.2.1. The Relationship "HasSUPAEvents"
This is a mandatory aggregation that defines the set of
SUPABooleanClauses that are aggregated by this SUPAECAPolicyRule
to form an Event clause. The multiplicity of this relationship is
0..1 on the aggregate (SUPAECAPolicyRule) side, and 1..n on the
part (SUPABooleanClause) side. This means that one or more
SUPABooleanClauses are aggregated and used to define this
SUPAECAPolicyRule. The 0..1 cardinality on the SUPAECAPolicyRule
side is necessary to enable SUPABooleanClauses to exist (e.g., in
a PolicyRepository) before they are used by a SUPAECAPolicyRule.
6.4.2.2. The Relationship "HasSUPAConditions"
This is a mandatory aggregation that defines the set of
SUPABooleanClauses that are aggregated by this SUPAECAPolicyRule
to form a Condition clause. The multiplicity of this relationship
is 0..1 on the aggregate (SUPAECAPolicyRule) side, and 1..n on the
part (SUPABooleanClause) side. This means that one or more
SUPABooleanClauses are aggregated and used to define this
SUPAECAPolicyRule. The 0..1 cardinality on the SUPAECAPolicyRule
side is necessary to enable SUPABooleanClauses to exist (e.g., in
a PolicyRepository) before they are used by a SUPAECAPolicyRule.
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6.4.2.3. The Relationship "HasSUPAActions"
This is a mandatory aggregation that defines the set of
SUPABooleanClauses that are aggregated by this SUPAECAPolicyRule
to form an Action clause. The multiplicity of this relationship is
0..1 on the aggregate (SUPAECAPolicyRule) side, and 1..n on the
part (SUPABooleanClause) side. This means that one or more
SUPABooleanClauses are aggregated and used to define this
SUPAECAPolicyRule. The 0..1 cardinality on the SUPAECAPolicyRule
side is necessary to enable SUPABooleanClauses to exist (e.g., in
a PolicyRepository) before they are used by a SUPAECAPolicyRule.
6.5. SUPAPolicyStatement Subclasses
Section 5.5.2 defines a common subclass of SUPAPolicyStatement,
called SUPAEncodedClause, which any SUPAPolicy (rule or predicate)
can use. This section describes another specialization of the
SGPIM SUPAPolicyStatement class for use in constructing (only)
SUPAECAPolicyRule objects.
6.5.1. Designing SUPAPolicyStatements Using SUPABooleanClauses
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. This
design is based on the DEN-ng model [2]. For example, this enables
the following Boolean clause to be defined:
Foo >= Bar
where Foo is a PolicyVariable, >= is a PolicyOperator, and Bar is
a PolicyValue. Note that in this approach, each of these three
terms (i.e., the PolicyVariable, PolicyOperator, and PolicyValue)
are subclasses of the EPRIM (specifically, of the
SUPABooleanClauseAtomic class, which is defined in Section 6.7.1).
This enables the EPRIM, in conjunction with the SGPIM, to be
used as a reusable class library. Put another way, this encourages
interoperability, since each element of the clause is itself an
object defined by SUPA.
The addition of a negation in the above statement is provided by
the supaTermIsNegated Boolean class attribute.
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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 subclasses of SUPABooleanClause.
These are called SUPABooleanClauseAtomic and
SUPABooleanClauseComposite, and are defined in Sections 6.7.1 and
6.7.2, respectively. This enables instances of either a
SUPABooleanClauseAtomic and/or a SUPABooleanClauseComposite to be
aggregated into a SUPABooleanClauseComposite object.
6.6. The Abstract Class "SUPABooleanClause"
This is a mandatory abstract class that defines a clause as the
following three-tuple:
{PolicyVariable, PolicyOperator, PolicyValue}
The composite pattern [3] is used in order to construct complex
Boolean clauses from a set of SUPABooleanClause objects. This is
why SUPABooleanClause is defined to be abstract - only instances
of the SUPABooleanAtomic and/or SUPABooleanComposite classes can
be used to construct a SUPABooleanClause.
Figure 8 below shows the composite pattern applied to the
SUPABooleanClause class.
1..n +-------------------+
\| |
+--------------- | SUPABooleanClause |
| /| |
| +-------------------+
| / \
| HasSUPABooleanClauses |
| |
| +----------------+---------+
/ \ | |
A | |
0..1 \ / | |
+----------------+---------+ +-----------+-----------+
|SUPABooleanClauseComposite| |SUPABooleanClauseAtomic|
+--------------------------+ +-----------------------+
Figure 8. The Composite Pattern Applied to a SUPABooleanClause
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The advantage of a SUPABooleanClause is that it is formed entirely
from SUPAPolicy objects. This enhances both reusability as well as
interoperability. Since this involves compositing a number of
objects, data model implementations MAY optimize a
SUPABooleanClause according to their application-specific needs
(e.g., by flattening the set of classes that make up a
SUPABooleanClause object into a single object).
6.6.1. SUPABooleanClause Attributes
The following sections define attributes of a SUPABooleanClause.
6.6.1.1. The Attribute "supaBoolIsNegated"
This is a mandatory Boolean attribute. If the value of this
attribute is TRUE, then this SUPABooleanClause is negated.
6.6.2. SUPABooleanClause Relationships
The following subsections define the relationships of a
SUPABooleanClause.
6.6.2.1. The Relationship "HasSUPABooleanClauses"
This is a mandatory aggregation that defines the set of
SUPABooleanClauses that are aggregated by this SUPABooleanClauseComposite to form a complete SUPABooleanClause
from multiple clauses (which can be made up of
SUPABooleanClauseAtomic and/or SUPABooleanClauseComposite object
instances. 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.
6.7. SUPABooleanClause Subclasses
SUPABooleanClause defines two subclasses, as shown in Figure 8.
They are both described in the following subsections.
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6.7.1. The Abstract Class "SUPABooleanClauseAtomic"
This is a mandatory abstract 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.
No attributes are currently defined for the
SUPABooleanClauseAtomic class. Its primary purpose is to
aggregate SUPAPolicyVariable, SUPAPolicyOperator, and
SUPAPolicyValue objects to form a complete SUPABoolean clause. As
such, this class is defined as abstract to simplify data model
optimization and mapping.
The three primary subclasses of the SUPABooleanClauseAtomic class
are shown in Figure 9.
+-------------------------+
| SUPABooleanClauseAtomic |
+-------------------------+
/ \
|
|
+-------------+--+-----------+
| | |
| | |
+----------+---------+ | |
| SUPAPolicyVariable | | |
+--------------------+ | |
| |
+----------+---------+ |
| SUPAPolicyOperator | |
+------------------- + |
|
+--------+--------+
| SUPAPolicyValue |
+---------------- +
Figure 9. SUPABooleanClauseAtomic Subclasses
6.7.1.1. The Abstract Class "SUPAPolicyVariable"
This is a mandatory abstract class. It is similar to the
PolicyVariable class of [RFC3460], but there are some important
differences in the SUPA version of this class that make the SUPA
version more generic than the version defined in [RFC3460]. The
problems in the definition of the [RFC3460] version of this class
are discussed in Section 6.7.1.1.1, and the SUPAPolicyVariable
class definition is defined in Section 6.7.1.1.2.
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6.7.1.1.1. Problems with the RFC3460 Version of PolicyVariable
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
SUPAPolicyVariable definition.
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
broader things than "just" a flow or an event. This is reflected
in the SUPAPolicyVariable definition.
Third, in [RFC3460], defining constraints for a variable is
limited to associating the variable with a PolicyValue. This is
both cumbersome (because associations are costly), 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 a generic SUPAConstraint object.
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)
6.7.1.1.2. The Abstract Class "SUPAPolicyVariable"
To be finished in the next version of this document.
The big question to be answered is whether to keep the
PolicyImplicitVariable and PolicyExplicitVariable subclasses of
[RFC3460] or not.
6.7.1.2. The Concrete Class "SUPAPolicyOperator"
This is a mandatory abstract class. Note that there is no
equivalent to this class in [RFC3460], which causes a number of
problems in the overloading of the semantics of an operator for
defining clauses in an ECA policy rule.
This will be defined in the next version of this document.
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6.7.1.3. The Abstract Class "SUPAPolicyValue"
This is a mandatory abstract class. It is similar to the
PolicyValue class of [RFC3460], but there are some important
differences in the SUPA version of this class that make the SUPA
version more generic than the version defined in [RFC3460]. The
problems in the definition of the [RFC3460] version of this class
are discussed in Section 6.7.1.3.1, and the SUPAPolicyVariable
class definition is defined in Section 6.7.1.3.2.
6.7.1.3.1. Problems with the RFC3460 Version of PolicyValue
This will be defined in the next version of this document.
6.7.1.3.2. The Abstract Class "SUPAPolicyValue"
This will be defined in the next version of this document.
6.7.2. The Abstract Class "SUPABooleanClauseComposite"
This will be defined in the next version of this document.
6.7.2.1. SUPABooleanClauseComposite Attributes
This will be defined in the next version of this document.
6.7.2.2. SUPABooleanClauseComposite Relationships
This will be defined in the next version of this document.
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7. SUPA GoalPredicate Information Model
This section defines the classes, attributes, and relationships of
the GPIM.
7.1. Overview
A Goal policy rule (also called a declarative policy rule, or an
intent-based policy rule) is a declarative statement that defines
what the policy should do, but not how to implement the policy. In
this draft, such rules are called SUPAGoalPredicates.
7.2. Constructing a SUPAGoalPredicate
This will be defined in the next version of this document.
7.3. Working With SUPAGoalPredicates
This will be defined in the next version of this document.
7.4. The Abstract Class "SUPAGoalPredicate"
This will be defined in the next version of this document.
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: TBD.
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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
[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
[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.
[RFC6021] Schoenwaelder, J., "Common YANG Data Types", RFC 6021,
October 2010.
11.2. Informative References
[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, v2.43,
http://dmtf.org/standards/cim/cim_schema_v2430
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Authors' Addresses
John Strassner
Huawei Technologies
2330 Central Expressway
Santa Clara, CA 95138 USA
Email: john.sc.strassner@huawei.com
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