One document matched: draft-snell-atompub-link-extensions-05.xml
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<rfc category="info" ipr="trust200811" updates="4287" docName="draft-snell-atompub-link-extensions-05.txt">
<front>
<title abbrev="Atom Link Extensions">Atom Link Extensions</title>
<author initials="J.M." surname="Snell" fullname="James M Snell">
<organization></organization>
<address>
<postal>
<street></street>
<city></city> <region></region> <code></code>
<country></country>
</postal>
<phone></phone>
<email>jasnell@us.ibm.com</email>
<uri>http://ibm.com</uri>
</address>
</author>
<date month="May" year="2010" />
<area>General</area>
<keyword>I-D</keyword>
<keyword>Internet-Draft</keyword>
<keyword>XML</keyword>
<keyword>Extensible Markup Language</keyword>
<keyword>Atom</keyword>
<keyword>RSS</keyword>
<keyword>Syndication</keyword>
<abstract><t>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.</t></abstract>
</front>
<middle>
<section title="Introduction">
<t>This specification adds additional attribute to the Atom Syndication Format
<xref target="RFC4287" /> link and content elements that may be used to express
additional metadata about linked resources.</t>
</section>
<section title="Notational Conventions">
<t>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, <xref target="RFC2119" /></t>
<t>This specification uses XML Namespaces <xref target="W3C.REC-xml-names-19990114"/>
to uniquely identify XML element names. It uses the following namespace prefix
for the indicated namespace URI;</t>
<figure><artwork><![CDATA[
"atom": "http://www.w3.org/2005/Atom"
]]></artwork></figure>
</section>
<section title="Hash Attributes">
<section title="Computing Hash Digests">
<t>When the resource referenced by atom:link or atom:content elements is
retrievable using HTTP, hash digest values are computed by first performing
an HTTP GET request on the URL specified by the @href or @src attributes,
extracting the returned entity-body, then following the steps specified in
Section 14.15 of <xref target="RFC2616" />.</t>
<t>It should be noted, however, that there are a variety of factors that
influence whether the entity-body returned by the HTTP GET will yield a
hash digest value matching that specified by a hash attribute contained
by the atom:link or atom:content elements. Accordingly, hash attribute
values MUST be considered to be strictly advisory and cannot be used
reliably as an end-to-end integrity check.</t>
</section>
<section title="The 'hash' attributes">
<t>The 'hash' Attribute specifies a whitespace-delimited list of hash digest values
calculated over the resource identified by the atom:link/@href or
atom:content/@src attributes. Each digest value is represented as a token identifying
the hash algorithm and the hex-encoded digest separated by an ASCII colon (":").
The 'hash' attribute MAY appear as a child of the atom:link and atom:content elements.</t>
<figure><artwork><![CDATA[
hash = attribute hash { digest-list }
digest-value = token ":" 1*HEXDIG
digest-list = digest-value *( LWSP digest-value )
]]></artwork></figure>
<t>An example MD5 and SHA-256 digests of an enclosed MP3 file:</t>
<figure><artwork><![CDATA[
<atom:link rel="enclosure"
href="http://example.org/media/myfile.mp3"
hash="md5:9e107d9d372bb6826bd81d3542a419d6
sha-256:6bf05cbbde96d6...d5ffe91e29272d805c98b988dc" />
]]></artwork></figure>
<t>This specification defines the following hash algorithm tokens: "md2",
"md5", "sha-1", "sha-224", "sha-256", "sha-384", and "sha-512". Additional
hash algorithms MAY be used.</t>
</section>
</section>
<section title="The 'etag' attribute">
<t>The 'etag' Attribute specifies an Entity Tag <xref target="RFC2616"/> 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.</t>
<figure><artwork><![CDATA[
etag = attribute le:etag { entity-tag }
entity-tag = [ weak ] opaque-tag
weak = "W/"
opaque-tag = quoted-string
]]></artwork></figure>
<t>An example weak entity tag for an enclosed MP3 file:</t>
<figure><artwork><![CDATA[
<atom:link rel="enclosure"
href="http://example.org/media/myfile.mp3"
etag='W/"xyzzy"' />
]]></artwork></figure>
<t>Note that HTTP defines the Entity Tag production such that quotes are
significant. For example, the values "W/xyzzy" and W/"xyzzy" represent two
distinctly different Entity Tags, the former being considered a "strong"
entity tag, the latter a "weak" entity tag. The etag attribute value MUST
include the appropriate double quotation marks.</t>
<t>The presence and placement of the quotes in the entity tag value can
introduce some difficulty when inserting the value into the etag attribute.
Producers of Atom documents must either use single quotes when specifying
the value of the etag attribute, e.g. etag='W/"xyzzy"' or use the "
entity reference to escape the double quotes within the etag value, e.g.
etag="W/"xyzzy"". A strong entity tag would be encoded as either
etag='"xyzzy"' or etag=""xyzzy"".</t>
</section>
<section title="The 'modified' attribute">
<t>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
<xref target="RFC3339" />. 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.</t>
<figure><artwork><![CDATA[
modified = attribute modified { xsd:dateTime }
]]></artwork></figure>
<t>An example last-modified attribute for an enclosed MP3 file:</t>
<figure><artwork><![CDATA[
<atom:link rel="enclosure"
href="http://example.org/media/myfile.mp3"
modified="2010-12-12T12:12:12Z" />
]]></artwork></figure>
</section>
<section title="The 'media' attribute">
<t>The 'media' attribute identifies the optimum media for the resource identified
by the atom:link/@href attribute. The value MUST be a valid media query as
specified by the Media Queries Specification [TODO: Link]. The media attribute
MUST be considered to be purely advisory and identifies for which type of media the
resource in question was designed. The 'media' attribute MAY appear as a child
of the atom:link element.</t>
<figure><artwork><![CDATA[
media = attribute media { media-query }
]]></artwork></figure>
<t>An example media attribute on an atom:link element:</t>
<figure><artwork><![CDATA[
<atom:link rel="alternate"
href="http://example.org/media/index.html"
media="handheld and (min-width: 20em)" />
]]></artwork></figure>
</section>
<section title="Security Considerations">
<t>TBD</t>
</section>
<section title="IANA Considerations">
<t>No IANA actions are required by this document.</t>
</section>
</middle>
<back>
<references title="Normative References">
&rfc1864;
&rfc2119;
&rfc2616;
&rfc3339;
&rfc4287;
&xmlnames;
</references>
</back>
</rfc>| PAFTECH AB 2003-2026 | 2026-04-24 02:39:21 |