Network Working Group J. Snell
Internet-Draft October 2006
Expires: April 4, 2007
Atom License Extension
draft-snell-atompub-feed-license-10.txt
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Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This memo defines an extension to the Atom Syndication Format for
describing licenses associated with Atom feeds and entries.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Experimental Status . . . . . . . . . . . . . . . . . . . . 3
1.2. Notational Conventions . . . . . . . . . . . . . . . . . . 3
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2. The "license" link relation . . . . . . . . . . . . . . . . . . 3
2.1. Unspecified License Links . . . . . . . . . . . . . . . . . 4
2.2. Example . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3. Inherited Licenses . . . . . . . . . . . . . . . . . . . . 4
2.4. Relationship with the "atom:rights" element . . . . . . . . 5
3. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . . . 8
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1. Introduction
This document defines an extension to the Atom Syndication Format
that can be used to describe the explicit rights that have been
granted to consumers of an Atom feed or entry.
1.1. Experimental Status
Describing licenses using the mechanisms defined in this
specification is currently considered to be largely experimental.
While it is a common practice for feed publishers to associate
licenses with syndicated content, there are still very few feed
consumers that utilize such metadata and the effectiveness of doing
so is still largely unknown. As it is not yet certain how these
mechanisms will be used, implementations and feedback are encouraged.
1.2. 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].
1.3. Terminology
The term "link relation" refers to the value of the Atom link
elements "rel" attribute as defined in section 4.2.7.2 of [RFC4287].
The term "license" refers to a potentially machine-readable
description of explicit rights, and associated obligations, that have
been granted to consumers of an Atom feed or entry.
2. The "license" link relation
The "license" link relation can be used to associate licenses with a
feed or entry.
Feed and entry elements MAY contain any number of "license" link
relations but MUST NOT contain more than one with the same
combination of href and type attribute values. The IRI specified by
the link's 'href' attribute SHOULD be dereferenceable to return a
representation of the license. The license representation MAY be
machine readable.
Feeds and entries can be dual-licensed by including multiple
"license" link relations specifying different href attribute values.
If multiple license link relations are specified, each SHOULD contain
a title attribute specifying a human-readable label for the license.
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2.1. Unspecified License Links
A publisher can use an "unspecified license link" (a "license" link
relation with an href attribute value equal to
"http://purl.org/atompub/license#unspecified") to indicate that a
feed or license has not been explicitly linked to a license
description.
A feed or entry containing an unspecified license link MUST NOT
contain any other license link relations.
2.2. Example
<feed xmlns="http://www.w3.org/2005/Atom">
<id>http://www.example.com/myfeed</id>
<title>My Example Feed</title>
<updated>2005-07-28T12:00:00Z</updated>
<link href="http://www.example.com/myfeed" />
<link rel="license" type="application/rdf+xml"
href="http://creativecommons.org/licenses/by-nc/2.5/rdf" />
<rights>
Copyright (c) 2005. Some rights reserved. This feed
is licensed under a Creative Commons Attribute-NonCommercial
Use License. It contains material originally published by
Jane Smith at http://www.example.com/entries/1 under the
Creative Commons Attribute License.
</rights>
<author><name>James</name></author>
<entry>
<id>tag:entries.org,2005:1</td>
<title>Atom Powered Robots Run Amok</title>
<updated>2005-06-28T12:00:00Z</updated>
<link href="http://www.example.org/entries/1" />
<summary>Atom Powered Robots Run Amok</summary>
<author><name>Jane Smith</name></author>
<link rel="license" type="text/html"
href="http://creativecommons.org/licenses/by/2.5/" />
</entry>
</feed>
2.3. Inherited Licenses
The license on a feed MAY be inherited by entries. Generally, a more
specific license overrides the less specific license. More
specifically, if an entry has any license link relations at all,
including the "undefined" license, it does not inherit the license of
the feed. If an entry has no license link relations, it does inherit
the license of its parent feed(s). Since an entry may appear in
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multiple feeds, it may inherit multiple licenses. This is equivalent
to stating multiple licenses on the entry itself.
The license on an entry MAY be inherited by media resources
associated with the entry. Some media types have ways of including
license information, which always overrides the entry's licensing.
Thus, an agent searching to find entries that fall under a specific
license (e.g. search for entries containing pictures and the word
"knitting" where the entry is under any Creative Commons license)
MUST check the most granular license definition available, rather
than assume license inheritance without checking.
2.4. Relationship with the "atom:rights" element
License link relations are related to the "atom:rights" element in
that both are intended to communicate information about the rights
associated with an Atom document. Where the two differ, however, is
in the fact that "atom:rights" is intended strictly as a human-
readable assertion of rights held over a work while the license link
relation is intended to provide a potentially machine-readable
description of what rights have been granted to others. The two
constructs may overlap one another and conflicts could arise if they
are contradictory. It is important that publishers of Atom documents
ensure that the "atom:rights" and license link relations are
consistent with one another.
3. Security Considerations
When "license" link relations are used in Atom documents, the
security considerations specified in [RFC4287] Section 8 apply.
4. IANA Considerations
This specification defines one new Atom link relation type to be
registered in the IANA Registry of Link Relations as defined by
[RFC4287].
Attribute Value: license
Description: Specifies the IRI of a license associated with
the containing feed, entry or source element.
Expected display characteristics: None
Security considerations: When "license" link relations are used
in Atom documents, the security considerations for
handling links in Atom documents apply.
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5. References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4287] Nottingham, M., Ed. and R. Sayre, Ed., "The Atom
Syndication Format", RFC 4287, December 2005.
Appendix A. Acknowledgements
The author gratefully acknowledges the feedback from Mike Linksvayer,
Robin Cover, Lisa Dussealt, Bjorn Hohrmann, Frank Ellermann, and the
members of Atom Publishing Format and Protocol working group during
the development of this specification.
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Author's Address
James M Snell
Phone:
Email: jasnell@gmail.com
URI: http://www.snellspace.com
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Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
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INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
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Copyright Statement
Copyright (C) The Internet Society (2006). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
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