Atom Link Extensions
draft-snell-atompub-link-extensions-03.txt

Abstract

This specification adds additional attributes to the Atom Syndication Format link and content elements that may be used to express additional metadata about linked resources.

Status of this Memo

This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on November 13, 2010.

Copyright Notice

Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved.

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Table of Contents

1.  Introduction
2.  Notational Conventions
3.  The 'md5' attribute
4.  The 'etag' attribute
5.  The 'modified' attribute
6.  Security Considerations
7.  IANA Considerations
8.  Normative References
§  Author's Address

1.  Introduction

This specification adds additional attribute to the Atom Syndication Format [RFC4287] (Nottingham, M., Ed. and R. Sayre, Ed., “The Atom Syndication Format,” December 2005.) link and content elements that may be used to express additional metadata about linked resources.

2.  Notational Conventions

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 BCP 14, [RFC2119] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.)

This specification uses XML Namespaces [W3C.REC‑xml‑names‑19990114] (Hollander, D., Layman, A., and T. Bray, “Namespaces in XML,” January 1999.) to uniquely identify XML element names. It uses the following namespace prefix for the indicated namespace URI;

 "atom": "http://www.w3.org/2005/Atom"

3.  The 'md5' attribute

The 'md5' Attribute specifies a MD5 digest [RFC1864] (Myers, J. and M. Rose, “The Content-MD5 Header Field,” October 1995.) of the resource identified by the atom:link/@href or atom:content/@src attributes. The value is represented as a sequence of 32 hexadecimal digits. The 'md5' attribute MAY appear as a child of the atom:link and atom:content elements.

  md5 = attribute md5 { md5-digest }
  md5-digest   = <hex of 128 bit MD5 digest as per RFC 1864>

An example MD5 digest of an enclosed MP3 file:

  <atom:link rel="enclosure"
    href="http://example.org/media/myfile.mp3"
    md5="9e107d9d372bb6826bd81d3542a419d6" />

The MD5 digest is computed based on the content of the entity-body as specified by Section 14.15 of [RFC2616] (Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, “Hypertext Transfer Protocol -- HTTP/1.1,” June 1999.).

4.  The 'etag' attribute

The 'etag' Attribute specifies an Entity Tag [RFC2616] (Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, “Hypertext Transfer Protocol -- HTTP/1.1,” June 1999.) for the resource identified by the atom:link or atom:content element. The 'etag' attribute MAY appear as a child of the atom:link and atom: content elements.

  etag = attribute le:etag { entity-tag }

  entity-tag = [ weak ] opaque-tag
  weak       = "W/"
  opaque-tag = quoted-string

An example Entity Tag for an enclosed MP3 file:

  <atom:link rel="enclosure"
     href="http://example.org/media/myfile.mp3"
     etag="W/xyzzy" />

5.  The 'modified' attribute

The 'modified' Attribute specifies the date and time when the resource identified by the atom:link or atom:content element was last modified. The value MUST conform to the "date-time" production defined by [RFC3339] (Klyne, G., Ed. and C. Newman, “Date and Time on the Internet: Timestamps,” July 2002.). An uppercase "T" character MUST be used to separate date and time, and an uppercase "Z" character MUST be present in the absence of a numeric time zone offset. The 'modified' attribute MAY appear as a child of the atom:link and atom:content elements.

  modified = attribute modified { xsd:dateTime }

An example last-modified attribute for an enclosed MP3 file:

  <atom:link rel="enclosure"
    href="http://example.org/media/myfile.mp3"
    modified="2010-12-12T12:12:12Z" />

6.  Security Considerations

TBD

7.  IANA Considerations

No IANA actions are required by this document.

8. Normative References

Author's Address