One document matched: draft-mehta-atom-inline-00.txt
Network Working Group N. Mehta
Internet-Draft Oracle Corp.
Intended status: Experimental June 9, 2009
Expires: December 11, 2009
In-lining Extensions for Atom
draft-mehta-atom-inline-00
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Abstract
This specification defines mechanisms for in-lining representations
of linked resources in Atom documents.
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Editorial Note
To provide feedback on this Internet-Draft, join the atom-syntax
mailing list (http://www.imc.org/atom-syntax/) [1].
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Namespace . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Notational Conventions . . . . . . . . . . . . . . . . . . 3
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2. In-line Representation of Resources . . . . . . . . . . . . . . 3
2.1. The "ae:inline" Extension Element . . . . . . . . . . . . . 4
2.1.1. Empty "ae:inline" Element . . . . . . . . . . . . . . . 5
2.1.2. The "type" Attribute . . . . . . . . . . . . . . . . . 6
2.1.3. Processing Model . . . . . . . . . . . . . . . . . . . 6
3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Feed with in-line replies link . . . . . . . . . . . . . . 7
3.2. Entry with in-line up link . . . . . . . . . . . . . . . . 8
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1. Normative References . . . . . . . . . . . . . . . . . . . 8
5.2. Informative References . . . . . . . . . . . . . . . . . . 9
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . . 9
Appendix B. Revision History . . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
This document defines an extension for in-line representations of
linked resources within the Atom Syndication Format [RFC4287]. Such
in-line representations can be either text, binary, or well-formed
XML.
1.1. Namespace
The XML Namespaces URI for the XML data format described in this
specification is:
http://purl.org/atom/ext/
This specification uses the prefix "ae:" for the namespace name. The
prefix "atom:" is used for "http://www.w3.org/2005/Atom", the
namespace name of the Atom Syndication Format [RFC4287]. These
namespace prefixes are not semantically significant.
1.2. Notational Conventions
Some sections of this specification are illustrated with fragments of
a non-normative RELAX NG Compact schema [RELAXNG]. In those
sections, this specification uses the xhtmlDiv, atomCommonAttributes,
atomMediaType and anyElement, defined in [RFC4287].
However, the text of this specification provides the definition of
conformance.
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 [RFC2119].
1.3. Terminology
This specification uses Atom link relations to identify different
types of links; see the Atom specification [RFC4287] for information
about their syntax, and the IANA link relation registry for more
information about specific values.
2. In-line Representation of Resources
Some applications require the ability to pre-fetch resources linked
from an Atom document using the atom:link element [RFC4287]. Such
in-line representations are similar to the in-line content model of
Atom.
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An Atom document MAY include the in-line representation of a linked
resource by using the ae:inline element inside the corresponding
atom:link element. The in-lined representation is only a hint and
MAY differ from the representation obtained from the URI referenced
in the link. Atom Processors SHOULD use the link URI to obtain the
complete representation of the linked resource.
2.1. The "ae:inline" Extension Element
The "ae:inline" element contains an approximate representation of the
linked resource.
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extensionInlineTextRepresentation =
element ae:inline {
atomCommonAttributes,
attribute type {"text" | "html"}?,
(text)*
}
extensionInlineXHTMLRepresentation =
element ae:inline {
atomCommonAttributes,
attribute type {"xhtml"},
xhtmlDiv
}
extensionInlineAtomRepresentation =
element ae:inline {
atomCommonAttributes,
attribute type {"feed" | "entry"},
atomFeed | atomEntry
}
extensionInlineOtherRepresentation =
element ae:inline {
atomCommonAttributes,
attribute type { atomMediaType }?,
(text|anyElement)*
}
extensionInlineEmpty =
element ae:inline {
atomCommonAttributes,
empty
}
extensionInline = extensionInlineTextRepresentation
| extensionInlineXHTMLRepresentation
| extensionInlineAtomRepresentation
| extensionInlineOtherRepresentation
| extensionInlineEmpty
2.1.1. Empty "ae:inline" Element
The ae:inline element may be empty if the producer of the Atom
document a linked resource cannot be in-lined, e.g., due to
inadequate authorization or if the resource does not yet exist.
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2.1.2. The "type" Attribute
On the ae:inline element, the value of the "type" attribute MAY be
one of "text", "html", "xhtml", "entry", or "feed". Failing that, it
MUST conform to the syntax of a MIME media type, but MUST NOT be a
composite type (see Section 4.2.6 of [RFC4288]). If the type
attribute is not provided, Atom Processors MUST behave as though the
type attribute were present with a value of "text".
The type attributes on an atom:link element and its nested ae:inline
element may not match.
2.1.3. Processing Model
Use of the in-line extensions MUST conform to the following rules.
Conforming Atom Processors MUST interpret ae:inline according to the
first applicable rule:
1. If the value of "type" is "text", the content of ae:inline MUST
NOT contain child elements. Such text is intended to be
presented to humans in a readable fashion. Thus, Atom Processors
MAY collapse white space (including line breaks), and display the
text using typographic techniques such as justification and
proportional fonts.
2. If the value of "type" is "html", the content of ae:inline MUST
NOT contain child elements and SHOULD be suitable for handling as
HTML [HTML]. The HTML markup MUST be escaped; for example,
"<br>" as "<br>". The HTML markup SHOULD be such that it
could validly appear directly within an HTML <DIV> element. Atom
Processors that display the content MAY use the markup to aid in
displaying it.
3. If the value of "type" is "xhtml", the content of ae:inline MUST
be a single XHTML div element [W3C.REC-XHTML] and SHOULD be
suitable for handling as XHTML. The XHTML div element itself
MUST NOT be considered part of the content. Atom Processors that
display the content MAY use the markup to aid in displaying it.
The escaped versions of characters such as "&" and ">" represent
those characters, not markup.
4. If the value of "type" is "entry", the content of atom:content
MUST be a single ATOM entry element [RFC4287].
5. If the value of "type" is "feed", the content of atom:content
MUST be a single ATOM feed element [RFC4287].
6. If the value of "type" is an XML media type [RFC3023] or ends
with "+xml" or "/xml" (case insensitive), the content of ae:
inline MAY include child elements and SHOULD be suitable for
handling as the indicated media type. This would normally mean
that the "ae:inline" element would contain a single child element
that would serve as the root element of the XML document of the
indicated type.
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7. If the value of "type" begins with "text/" (case insensitive),
the content of ae:inline MUST NOT contain child elements.
8. For all other values of "type", the content of atom:content MUST
be a valid Base64 encoding, as described in [RFC3548], 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:content element by white
space, and lines are separated by a single newline (U+000A)
character.
3. Examples
3.1. Feed with in-line replies link
<feed xmlns="http://www.w3.org/2005/Atom"
xmlns:thr="http://purl.org/syndication/thread/1.0">
<id>http://www.example.org/entries</id>
<title>My posts</title>
<updated>2006-03-01T12:12:12Z</updated>
<link rel="replies" thr:count="10"
href="http://www.example.org/replies">
<ae:inline xmlns:ae="http://purl.org/atom/ext/"
type="feed">
<feed>
...
</feed>
</ae:inline>
</link>
<link rel="self"
href="http://www.example.org/entries" />
...
</feed>
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3.2. Entry with in-line up link
<entry xmlns="http://www.w3.org/2005/Atom">
<link rel="up" type="application/atom+xml"
href="/finance/feeds/default/portfolios/1">
<ae:inline type="entry">
<atom:entry>
...
</atom:entry>
</ae:inline>
</atom:link>
<atom:link rel="edit"
href="/finance/feeds/default/portfolios/1/positions/NASDAQ:ORCL"/>
...
</atom:entry>
4. Security Considerations
In-line Extensions for Atom are subject to the security
considerations found in Section 8 of [RFC4287].
In-line representations can overwhelm Atom processors. For this
reason, consumers of Atom representations should take adequate
precautions to limit resource consumption when processing ae:inline
elements.
5. References
5.1. Normative References
[HTML] Raggett, D., Hors, A., and I. Jacobs, "HTML 4.01
Specification, W3C REC REC-html401-19991224",
December 1999,
<http://www.w3.org/TR/1999/REC-html401-19991224>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media
Types", RFC 3023, January 2001.
[RFC3548] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 3548, July 2003.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
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RFC 3986, January 2005.
[RFC4287] Nottingham, M., Ed. and R. Sayre, Ed., "The Atom
Syndication Format", RFC 4287, December 2005.
[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and
Registration Procedures", BCP 13, RFC 4288, December 2005.
[W3C.REC-XHTML]
Pemberton, S., "XHTML 1.0: The Extensible HyperText Markup
Language", W3C REC-XHTML, January 2000,
<http://www.w3.org/TR/xhtml1/>.
5.2. Informative References
[RELAXNG] Clark, J., "RELAX NG Compact Syntax", December 2001, <http
://www.oasis-open.org/committees/relax-ng/
compact-20021121.html>.
URIs
[1] <http://www.imc.org/atom-syntax/>
Appendix A. Acknowledgements
On the atom-syntax mailing list, Hadrien Gardeur, Al Brown, Julian
Reschke, Mark Nottingham, Pablo Castro, Kyle Marvin, and James Snell
provided very valuable feedback to solidify this draft.
Appendix B. Revision History
00 - Initial Revision, split from draft-divilly-atom-hierarchy-01.
Author's Address
Nikunj R. Mehta
Oracle Corp.
Email: nikunj.mehta@oracle.com
URI: http://o-micron.blogspot.com/
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