The Atom Link "inline" Extension
draft-snell-atompub-inline-00.txt

Abstract

This specification adds a mechanism to the Atom Syndication Format which publishers of Atom Feed and Entry documents can use to embed representations of linked resources into a child element of the atom:link element.

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 February 23, 2011.

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 'atom:inline' element
4.  Security Considerations
5.  IANA Considerations
6.  Acknowledgements
7.  Normative References
§  Author's Address

1.  Introduction

TBD

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., Bray, T., and A. Layman, “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 'atom:inline' element

The atom:inline element MAY be used as the child of an atom:link element to embed representations of the resource referenced by the containing atom:link.

  inline = element atom:inline {
    atomCommonAttributes,
    attribute type { atomMediaType }?,
    (text|anyElement)*
  }

The atom:inline element MAY contain a type attribute whose value specifies the MIME media type of the representation contained by the element. If the type attribute is not provided, Atom Processors MUST behave as though the type attribute were present with a value equal to that specified by the containing atom:link elements type attribute. The value of the type attribute MUST NOT be a composite type as specified by Section 4.2.6 of [MIMEREG].

An atom:link element MAY contain any number of atom:inline elements, but MUST NOT contain more than one with the same type attribute value.

If the value of the type attribute begins with "text/" (case insensitive), the content of atom:inline MUST NOT contain child elements.

If the value of the type attribute is an XML media type [RFC3023] (Murata, M., St. Laurent, S., and D. Kohn, “XML Media Types,” January 2001.) or ends with "+xml" or "/xml" (case insensitive), the content of the atom:inline element MAY include child elements and SHOULD be suitable for handling as the indicated media type. This would normally mean that the atom:inline element would contain a single child element that would serve as the root element of the XML document of the indicated type.

For all other values of the type attribute, the content of atom:inline MUST be a valid Base64 encoding, as described in [RFC3548] (Josefsson, S., “The Base16, Base32, and Base64 Data Encodings,” July 2003.), section 3. When decoded, it SHOULD be suitable for handling as the indicated media type. In this case, the characters in the Base64 encoding MAY be preceded and followed in the atom:inline element by white space, and lines are separated by a single newline (U+000A) character.

  <feed xmlns="http://www.w3.org/2005/Atom">
     ...
     <entry>
       ...
       <link rel="alternate" type="text/plain" href="example.txt">
         <inline>This is an example</inline>
       </link>
       <link rel="self" type="application/json" href="entry.json">
         <inline>ew0KICAiaWQiOiJodHRwOi8vZXhhbXBsZS5vcm
cvZm9vIiwNCiAgInRpdGxlIjoiZm9vIg0KfQ==</inline>
       </link>
       ...
     </entry>
     ...
  </feed>

The atom:inline element MAY have an xml:base attribute [W3C.REC‑xmlbase‑20010627] (Marsh, J., “XML Base,” June 2001.). When xml:base is used, it serves the function described in section 5.1.1 of [RFC3986] (Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax,” January 2005.), establishing the base URI (or IRI) for resolving any relative references found within the effective scope of the xml:base attribute.

The atom:inline element MAY have an xml:lang attribute, whose content indicates the natural language for the element and its descendents. Requirements regarding the content and interpretation of xml:lang are specified in XML 1.0 [W3C.REC‑xml‑20040204] (Maler, E., Paoli, J., Yergeau, F., Bray, T., and C. Sperberg-McQueen, “Extensible Markup Language (XML) 1.0 (Third Edition),” February 2004.), Section 2.12.

4.  Security Considerations

TBD

5.  IANA Considerations

TBD

6.  Acknowledgements

The author gratefully acknowledges the feedback from the members of the Atom Publishing Format and Protocol working group during the development of this specification.

7. Normative References

Author's Address