Network Working Group E. Wilde
Internet-Draft EMC Corporation
Intended status: Standards Track April 3, 2012
Expires: October 5, 2012
The 'describes' Link Relation Type
draft-wilde-describes-link-00
Abstract
This specification defines the 'describes' link relation type that
allows resource representations to indicate that they are describing
another resource. In contexts where applications want to associate
described resources and description resources, and want to build
services based on these associations, the 'describes' link relation
type provides the opposite direction of the 'describedby' link
relation type, which already is a registered link relation type.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Resource Descriptions . . . . . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
6. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . . 5
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 5
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1. Introduction
Resources on the Web can be identified by an (registered) URI scheme
and can be represented by any (registered) media type. In many
cases, applications establish specific (i.e., typed) relations
between the resources they are concerned with, which can be under
their control or controlled by another authority. A common pattern
for associating resources is to have resources which are descriptions
of other resources. This specification registers the 'describes'
link relation which allows applications to represent the fact that
one resource is a description of another resource.
RFC 5988 [1] "defines a framework for typed links that isn't specific
to a particular serialisation or application. It does so by
redefining the link relation registry established by Atom to have a
broader domain, and adding to it the relations that are defined by
HTML."
2. Terminology
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 RFC 2119 [2].
3. Resource Descriptions
Associating resources with descriptions of these resources is a
recurring pattern on the Web. The IANA link relation registry
established by RFC 5988 [1] currently contains a 'describedby' link
relation type, which has been registered by POWDER [3]. The
definition given in that registration is as follows: "The
relationship A 'describedby' B asserts that resource B provides a
description of resource A. There are no constraints on the format or
representation of either A or B, neither are there any further
constraints on either resource."
Since many scenarios using resource descriptions need to represent
the fact that some resource describes a resource (the opposite of the
'describedby' relation), this document registers a 'describes' link
relation type. Establishing a link A 'describes' B asserts that the
resource identified by A is a description of the resource identified
by B, without constraining in any way the identifiers being used for
A and B, and the media types for the representations being provided,
when those identifiers are dereferenced. Specifically, it is
possible that identifiers A and/or B have no associated interaction
method (they could be URNs, for example), but it still is valid to
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establish the A 'describes' B link.
Another design freedom is to use "chains" of 'describes' (or
'describedby') links, so that one resource is a description of
another resource, which in turn is a description of yet another
resource. The "levels" of descriptions can go as deep as required by
an application, and are not constrained by this specification.
4. IANA Considerations
The link relation type below has been registered by IANA per Section
6.2.1 of RFC 5988 [1]:
Relation Name: describes
Description: Identifying that a resource describes another
resource, without making additional claims of the described or
description resource.
Reference: RFC xxxx (this draft's eventual RFC number)
Notes: This link relation type is intended to be the inverse of
the already 'describedby' relation type, thus allowing links to be
established in both directions.
5. Security Considerations
Resource descriptions SHOULD never be treated as authoritative or
exclusive without relying on additional mechanisms for trust and
security. Resources can have many (possible conflicting)
descriptions, and the 'describes' link relation type makes no claim
whatsoever about the authority of the party providing the association
between the two resources, or about the authority of the party
providing the description resource.
6. Change Log
Note to RFC Editor: Please remove this section before publication.
7. References
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7.1. Normative References
[1] Nottingham, M., "Web Linking", RFC 5988, October 2010.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997.
7.2. Informative References
[3] Archer, P., Smith, K., and A. Perego, "Protocol for Web
Description Resources (POWDER): Description Resources", World
Wide Web Consortium Recommendation REC-powder-dr-20090901,
September 2009,
<http://www.w3.org/TR/2009/REC-powder-dr-20090901/>.
Appendix A. Acknowledgements
Thanks for comments and suggestions provided by ...
Author's Address
Erik Wilde
EMC Corporation
6801 Koll Center Parkway
Pleasanton, CA 94566
U.S.A.
Phone: +1-925-6006244
Email: erik.wilde@emc.com
URI: http://dret.net/netdret/
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