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.

Status of this Memo

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This Internet-Draft will expire on October 03, 2012.

Copyright Notice

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Table of Contents

• 1. Introduction
• 2. Terminology
• 3. Resource Descriptions
• 4. IANA Considerations
• 5. Security Considerations
• 6. Change Log
• 7. References
• 7.1. Normative References
• 7.2. Informative References
• Appendix A. Acknowledgements
• Author's Address

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 [RFC5988] "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 [RFC2119].

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 [RFC5988] currently contains a 'describedby' link relation type, which has been registered by POWDER [POWDER]. 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 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 [RFC5988]:

• 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

7.1. Normative References

7.2. Informative References

Appendix A. Acknowledgements

Thanks for comments and suggestions provided by ...

Author's Address