Network Working Group S. Hole
Internet Draft: ACAP A. Melnikov
ACI WorldWide/MessagingDirect
Document: draft-ietf-acap-option-04.txt June 2002
Expires in 6 months
ACAP Application Options Dataset Class
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Copyright Notice
Copyright (C) The Internet Society 2002. All Rights Reserved.
1. Introduction
The Application Configuration Access Protocol (ACAP) is designed to
support remote storage and access of application option,
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configuration and preference information. The generalized form of
this runtime configuration is called "options". Options consist of
any type of structured or unstructured data that an application
requires to operate in a user specific manner.
Storage of application options in an ACAP server substantially
solves the "kiosk user" problem for applications -- serial use of a
single machine by multiple users. It also solves the "nomadic
user" problem -- use of more than one machine on a regular basis by
a single user.
The specification defines the "option" dataset class for use with
ACAP.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
in this document are to be interpreted as described in [KEYWORDS].
The attribute syntax specifications use the Augmented Backus-Naur
Form (ABNF) notation as specified in [ABNF].
3. ACAP personal options
3.1. ACAP option representation
Individual options are represented as ACAP entries in option
datasets. The name of the entry, as defined by the "entry"
attribute for the entry, is the name of option.
3.2. Scalar options
Scalar options are ACAP entries that contain simple (unstructured)
data. The "option.value" attribute of the entry contains the data
for the option. The value can be single or multivalued.
Following is an example of a single and multivalued scalar option:
color.preferred
entry = "color.preferred"
option.value = "blue"
color.list
entry = "color.list"
option.value = ("red" "green" "blue" "cyan" "black")
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Scalar options that are intended to be used by multiple applica-
tions should be registered as defined in section 4.4.
3.3. Structured options
Structured options are ACAP entries that contain multiple related
items of data in a single option. Data for the option is contained
in multiple named attributes collectively called "field
attributes". Each field attribute can be single or multivalued.
Following is an example of a structured option:
color.definition
entry = "color.definition"
option.color.definition.name = "blue"
option.color.definition.rgb = ("blue=255" "red=0" "green=0")
option.color.definition.index = "66"
By definition, structured options are application specific. While
the content of the field attributes can be obtained by any applica-
tion, it's intended use is open to interpretation by the applica-
tion.
3.4. ACAP option hierarchy
Option sets MAY be represented using ACAP hierarchy. Any entry in
an option dataset can also be a hierarchy node by setting the "sub-
dataset" attribute. Applications can model arbitrarily structured
configuration information using hierarchical datasets containing
scalar or structured options. An option subdataset of scalar
options models an associative list. An option subdataset of struc-
tured options models an array of structures.
3.5. ACAP option attribute formal syntax
The naming conventions for option entry attributes is defined by
the following ABNF.
option-value-attr = scalar-option-attr / structured-option-attr
scalar-option-attr = "option.value"
structured-option-attr = "option." name-component
1*("." name-component)
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4. ACAP option namespace
The general ACAP namespace is organized to promote inheritance
between site, host, group, and user specific configuration informa-
tion, as defined in [ACAP]. It defines a "site", "group", "host",
and "user" second level hierarchy. The option dataset defines a
third level of hierarchy that promotes inheritance from second
level datasets, and isolates user and application specific
instances of configuration information.
4.1. ACAP "/option" dataset class
The dataset class whose name is "/option" is assumed to contain
option datasets as defined in this specification.
4.2. Third level option datasets
Third level option datasets break the option namespace into generic
and application specific option sets. This serves two purposes:
to promote the creation and inheritance of common options between
applications, and isolation of application specific configuration
from other applications.
4.2.1. The "vendor" option namespace
The "vendor" option namespace is a set of datasets, each named in
the form "vendor.<vendor-name>", where "<vendor-name>" is the name
of a specific application or application vendor.
The entries in the vendor namespace enumerate the applications that
make use of ACAP option storage at that level. Each vendor dataset
contains option entries and/or subdatasets for a specific vendor
applications. All options not in the "standard" namespace MUST be
in one of the "vendor" option namespaces.
The "vendor-name" for an application or vendor MUST be registered
with IANA according to the rules in section 5.1. The "ven-
dor.x-<vendor-name>" namespace is reserved for temporary use by
vendors during product development, or for local applications that
are not generally distributed.
Vendors are free to suballocate their namespace as they see fit.
For example, a vendor may chose to store options for the various
applications that it produces in subdatasets underneath their ven-
dor namespace. For example, the CoolStuff software company may
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chose to organize the option namespace for their software products
like
vendor.CoolStuff.caltool
vendor.CoolStuff.webtool
vendor.CoolStuff.mailtool
rather than try to register their application names as a vendor-
name in the vendor namespace.
4.2.2. The "standard" option namespace
The "standard" option namespace is a dataset named "standard" that
contains option entries that are generally applicable to a number
of applications. The namespace is reserved for shared options that
do not meet the requirements for a separate ACAP dataset class.
The standard option namespace is further partitioned into "standard
option classes" where option names are of the form "<standard-
option-class-prefix>.<option-name>". Standard option classes are
associated with a class of applications, e.g. mail user agents. The
"<standard-option-class-prefix>" is a registered string that
uniquely identifies the option class, e.g. "mua".
This document defines two standard option class prefixes - "common"
and "X". The "common" standard option class contains options that
are generally applicable to a large number of application classes.
For example, a default font or window background color. The "X"
namespace is reserved for temporary use by software developers dur-
ing product development.
Following are some examples of the standard option namespace:
standard/common.default.font
standard/common.default.color.background
standard/X.test-option
Option classes and names in the "standard" option namespace MUST be
registered with IANA according to the rules in section 5.2. Ven-
dors MUST NOT use the temporary namespace in products that are gen-
erally distributed.
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4.3. Example option namespace
The following example demonstrates how the "standard" and "vendor"
namespaces isolate application specific and standard configuration
within the standard ACAP dataset namespace hierarchy.
/option/
site/
standard/
vendor.<vendor-name-1>/
vendor.<vendor-name-2>/
...
...
host/
<host-1>/
standard/
vendor.<vendor-name-1>/
vendor.<vendor-name-2>/
...
...
<host-2>/
...
...
group/
<group-1>/
standard/
vendor.<vendor-name-1>/
vendor.<vendor-name-2>/
...
...
<group-2>/
...
...
user/
<user-1>/
standard/
vendor.<vendor-name-1>/
vendor.<vendor-name-2>/
...
...
<user-2>/
...
...
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4.4. Formal Syntax for the Option Dataset Namespace
The naming conventions for the option dataset are defined by the
standard ABNF in [ACAP] for dataset namespaces, constrained and/or
extended by the following ABNF.
dname-component = 1*UTF8-CHAR
;; MUST NOT begin with "." or contain "/"
name-component = 1*UTF8-CHAR
;; MUST NOT contain ".", "/", "%", or "*"
option-dataset = "/option/" owner
option-component = standard-component / vendor-component
owner = owner-site / owner-host / owner-group /
owner-user / "~/" option-component
owner-group = "group/" dname-component "/" option-component
owner-host = "host/" dname-component "/" option-component
owner-site = "site/" option-component
owner-user = "user/" dname-component "/" option-component
standard-component = "standard/" standard-option-class "."
name-component
;; The name-component MUST BE an IANA registered
;; option name under the option class.
standard-option-class = "common" / "X" / name-component
;; The name-component MUST BE an IANA registered
;; option class prefix.
vendor-component = vendor-name "/" dname-component
vendor-name = vendor-token *("." name-component)
vendor-token = "vendor." name-component
;; The name-component is the name of the
;; application or vendor organization to which
;; the options belong.
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5. Namespace registration procedures
Some portions of the ACAP option namespace are designed to be
extensible within the standard. The goals for extensibility
include: (1) minimal process to extend the namespace within the
standard, (2) promote interoperability within the namespace, and
(3) support experimentation and development within the namespace.
To support these requirements, the ACAP Option dataset draws on the
recommendations for registration policies and procedures outlined
in [IANA-CONSIDERATIONS].
5.1. Registering vendor names
The "vendor" option namespace is specifically designed to support
delegation of authority to individual organizations. The goal is
to provide a completely independent namespace for each application
vendor. The requirement is that each vendor namespace be uniquely
associated with one and only one vendor or product.
The "vendor" option namespace uses the identical registry as the
"vendor" dataset class defined in [ACAP]. Organizations that wish
to register a vendor name for the option namespace MUST follow the
procedures outlined in [ACAP].
5.2. Registering standard options
The "standard" option namespace requires standardization procedures
for two different types of object: standard option class prefixes
and standard option names.
Standard option class prefixes MUST be registered with IANA. New
option class proposals MUST be confirmed using IETF Consensus, pri-
marily through consultation on the ACAP implementors mailing list.
Registration of an option class MUST include a review contact that
is responsible for approving registrations for option names regis-
tered in the option class. Registrations MUST provide the follow-
ing information when requesting a new standard option class prefix.
To: iana@iana.org
Subject: Registration of ACAP standard option class
Requested standard option class name: <option-class-name>
Requested standard option class prefix: <option-class-prefix>
Requested standard option class short description:
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Approval contact: name, address, e-mail address, phone number
# as many contacts as appropriate - must be at least one
Standard option names MUST be registered with IANA using the Hier-
archical Allocation model described in [IANA-CONSIDERATIONS]. All
proposals MUST be reviewed and passed by the IANA registered con-
tact for the option class prior to submission. Discussion on new
option name proposals on the ACAP implementors mailing list is
strongly encouraged. Registrations MUST provide the following
information when requesting a new standard option name.
To: iana@iana.org
Subject: Registration of ACAP standard option
Containing option class: <option-class-name>
Requested option name: <option-class-prefix>.<option-name>
Option short description:
Value semantics: # any specific semantic restrictions placed
on the value of the option, e.g. URL,
integer, ...
Value default: # a recommended default value for the option
6. Recommendations for standardization
There are no absolute rules for when to register a set of standard
options vs. defining a new dataset class. In general, one can
always register a standard option class and a set of option names
under that class. In some cases, it MAY be appropriate to define a
new dataset class instead of registering a set of standard options.
The key distinguishing feature of a dataset class definition is its
documentation requirements. Dataset class definitions specify the
semantic relationships in the dataset class. The semantic rela-
tionships between subdatasets, entries and attributes are fully
defined and part of the standard.
If a set of standard options has any of the following characteris-
tics, then it should be considered a candidate for a new dataset
class.
1. The option set consists of a list (array) of identically struc-
tured options. Proper representation of option sets of this type
require a subdataset. This is not prohibited by the standard
option namespace, but the list relationship of the options needs to
be documented. This makes it appropriate for a new dataset class.
2. Many or all of the options are semantically related or dependent
on one another. Individual options are incomplete, or not useful
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unless evaluated in the context of the other options in the class.
The relationship or dependencies cannot be documented by individual
option registrations.
3. The set of options are interpreted by applications with addi-
tional semantic rules that apply to the set of options, and cannot
be documented in the registration information for individual stan-
dard options.
In summary, any standard option set that has semantic relationships
beyond a single option value is a candidate for a new dataset class
definition. Standard option sets SHOULD NOT be defined that have
additional semantic rules outside those of the individual options.
Standard option sets that acquire additional semantics over a
period of time, SHOULD be redefined as a dataset class using the
procedures and format outlined in [ACAP].
Note that these considerations apply only to options in the "stan-
dard" option namespace. Semantic relationships in the vendor
namespace are at the discretion of the vendor and are not consid-
ered part of the extended standardization content of the ACAP
option namespace.
7. Security Considerations
It is important to make sure that access controls are set correctly
on personal options. Sensitive configuration information, includ-
ing application security information, should not be exposed to
other users without an explicit request by the user.
This specification does not address storing private certificates
and other security information in the option namespace. This may
be added to a future version of this specification when more exper-
imentation has been done.
8. Acknowledgments
Many thanks to the following people who have contributed to devel-
opment of the option dataset class specification: Jack DeWinter,
Rob Earhart, Ned Freed, Randy Gellens, John Meyers, Chris Newman,
Lyndon Nerenberg, John-Paul Sicotte, Matt Wall and other partici-
pants of the IETF ACAP working group.
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9. References
[ABNF] Crocker, D., Overell, P., "Augmented BNF for Syntax Specifi-
cations: ABNF", RFC 2234, November 1997
<ftp://ftp.isi.edu/in-notes/rfc2234.txt>
[ACAP] Newman, C., Myers, J. G., "Application Configuration Access
Protocol", RFC 2244, November 1997.
<ftp://ftp.isi.edu/in-notes/rfc2244.txt>
[IANA-CONSIDERATIONS] Thomas Narten, Harald Tveit Alvestrand,
"Guidelines for Writing an IANA Considerations Section in RFCs",
RFC 2434, October 1998.
<ftp://ftp.isi.edu/in-notes/rfc2434.txt>
[KEYWORDS] Bradner, S., "Key words for use in RFC to Indicate
Requirement Levels", RFC 2119, March 1997.
<ftp://ftp.isi.edu/in-notes/rfc2119.txt>
10. Authors' Addresses
Steve Hole
mailto:Steve.Hole@messagingdirect.com
Alexey Melnikov
mailto:Alexey.Melnikov@messagingdirect.com
ACI WorldWide/MessagingDirect
900 10117 - Jasper Ave.
Edmonton, Alberta, T5J 1W8, CANADA
11. Full Copyright Statement
Copyright (C) The Internet Society 2002. All Rights Reserved.
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lished and distributed, in whole or in part, without restriction of
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ever, this document itself may not be modified in any way, such as
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