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<title>SWORD 002: AtomPub Extensions for Packaged Content</title>
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<h1>AtomPub Extensions for Packaged Content</h1>
<h2>Credits</h2>
<p>
<strong>SWORD 2.0 Technical Lead</strong>: Richard Jones, Cottage Labs
</p>
<p>
<strong>SWORD 2.0 Community Manager</strong>: Stuart Lewis, University of Auckland
</p>
<p>
<strong>SWORD 2.0 Technical Advisory Group</strong><br/>
Julie Allinson, University of York<br/>
Tim Brody, University of Southampton<br/>
David Flanders, JISC<br/>
Graham Klyne, University of Oxford<br/>
Alister Miles, University of Oxford<br/>
Ben O'Steen, Cottage Labs<br/>
Mark MacGillivray, Cottage Labs<br/>
Rob Sanderson, LANL<br/>
Nick Sheppard, Leeds Metropolitan University<br/>
Eddie Shin, MediaShelf<br/>
Ian Stuart, University of Edinburgh<br/>
Ed Summers, Library of Congress<br/>
David Tarrant, University of Southampton<br/>
Graham Triggs, BioMed Central<br/>
Scott Wilson, University of Bolton<br/>
</p>
<p>
<strong>Further acknowledgements of input</strong><br/>
Aaron Birkland (Cornell University), Tim Donohue (DuraSpace), Jim Downing (University of Cambridge), Ross Gardler (OSS Watch), Steve Midgley (US Department of Education), Glen Robson (National Library of Wales), Peter Sefton (University Of Southern Queensland), Adrian Stevenson (UKOLN), Paul Walk (UKOLN), Nigel Ward (University of Queensland)
</p>
<h2>Introduction</h2>
<p>
The Atom Publishing Protocol [<a href="#rfc5023">RFC5023</a>] defines how to create a Media
Resource by POSTing the media to a server. It deals exclusively with
the upload of a single file to the Media Entry, and does not make
explicit allowances for the possibility that this file may be a
package or bundle of other files in a particular format. This
specification covers extensions to the protocol to support this extra
condition.
</p>
<p>
This specification defines a set of extensions to the Atom Publishing
Protocol [<a href="#rfc5023">RFC5023</a>] to support the transfer and recovering of content
packages via the standard.
</p>
<h3>1.1 Terminology</h3>
<p>
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 RFC 2119 [<a href="#rfc2119">RFC2119</a>].
</p>
<h3>1.2 Namespaces</h3>
<p>All extensions are defined within the namespace:</p>
<div class="code">
http://purl.org/net/sword/
</div>
<p>This document uses the prefix <span class="code_inline">sword</span> for the namespace name.</p>
<p>The AtomPub namespace is:</p>
<div class="code">
http://www.w3.org/2007/app
</div>
<p>This document uses the prefix <span class="code_inline">app</span> for the namespace name.</p>
<p>The Atom Syndication Format namespace is:</p>
<div class="code">
http://www.w3.org/2005/Atom
</div>
<p>This document uses the prefix <span class="code_inline">atom</span> for the namespace name.</p>
<h2>2 Service Document Extensions</h2>
<p>This section documents extensions to the Atom Service Document.</p>
<h3>2.1 sword:mediation</h3>
<p>
The <span class="code_inline">sword:mediation</span> element MUST be used to determine if a Media
Collection will accept the deposit of content on behalf of a user
other than the authenticated depositor. If it is not present the
client MUST assume that the server does not support such mediated
deposit.
</p>
<p>
Traditional HTTP authentication is often insufficient during packaged content
deposit, as it is possible that content will be delivered machine-to-
machine and the authenticating user will be the client not the
content owner. The presence of the <span class="code_inline">sword:mediation</span> element, which
MUST take a <span class="code_inline">true</span> or <span class="code_inline">false</span> value, indicates whether the
<span class="code_inline">On-Behalf-Of</span> HTTP header [<a href="#sword001">SWORD001</a>] can be used to provide the server with a
user other than the authenticated one who should be considered the
actor in the transfer.
</p>
<p>For example:</p>
<div class="code">
<pre>
&lt;service xmlns="http://www.w3.org/2007/app"
xmlns:sword="http://purl.org/net/sword/terms/"
xmlns:atom="http://www.w3.org/2005/Atom"&gt;
&lt;workspace&gt;
&lt;atom:title&gt;Main Site&lt;/atom:title&gt;
&lt;collection href="http://www.appserver.org/col1"&gt;
&lt;atom:title&gt;Collection 1&lt;/atom:title&gt;
&lt;accept&gt;*/*&lt;/accept&gt;
&lt;sword:mediation&gt;true&lt;/sword:mediation&gt;
&lt;/collection&gt;
&lt;/workspace&gt;
&lt;/service&gt;
</pre>
</div>
<h3>2.2 sword:acceptPackaging</h3>
<p>
The <span class="code_inline">sword:acceptPackaging</span> element SHOULD be used to indicate to the
client what package formats are acceptable to send to the server.
If the server does not supply an element, the client MUST assume
that the server only supports an ordinary, unstructured zip file.
The server MAY unzip any such files, or MAY store them as opaque
binary files. The <span class="code_inline">sword:acceptPackaging</span> element MUST contain a URI
identifying the packaging format.
</p>
<p>For example:</p>
<div class="code">
<pre>
&lt;service xmlns="http://www.w3.org/2007/app"
xmlns:sword="http://purl.org/net/sword/terms/"
xmlns:atom="http://www.w3.org/2005/Atom"&gt;
&lt;workspace&gt;
&lt;atom:title&gt;Main Site&lt;/atom:title&gt;
&lt;collection href="http://www.appserver.org/col1"&gt;
&lt;atom:title&gt;Collection 1&lt;/atom:title&gt;
&lt;accept&gt;*/*&lt;/accept&gt;
&lt;sword:acceptPackaging&gt;
http://purl.org/net/sword/package/BagIt
&lt;/sword:acceptPackaging&gt;
&lt;sword:acceptPackaging&gt;
http://purl.org/net/sword/package/METSDSpaceSIP
&lt;/sword:acceptPackaging&gt;
&lt;/collection&gt;
&lt;/workspace&gt;
&lt;/service&gt;
</pre>
</div>
<h2>3 Media Entry Extensions</h3>
<p>
This section documents extensions to the Media Entry document which
can be retrieved from the server from the Media Entry URI.
</p>
<h3>3.1 sword:packaging</h3>
<p>
The <span class="code_inline">sword:packaging</span> element SHOULD be used by the server to indicate
the packaging formats that it is capable of delivering the Media
Resource to the client in. If there is no <span class="code_inline">sword:packaging</span>
element, the client MUST NOT assume any packaging format; instead
it must rely on the <span class="code_inline">atom:content@type</span> as normal, per [<a href="#rfc5023">RFC5023</a>]. If a
<span class="code_inline">sword:packaging</span> element is provided the client MAY request the
<span class="code_inline">atom:content@src</span> URI with the <span class="code_inline">Packaging</span> HTTP header [<a href="#sword001">SWORD001</a>]
containing the value of the <span class="code_inline">sword:packaging</span> element.
</p>
<p>
The value of the <span class="code_inline">sword:packaging</span> element MUST contain a URI
identifying the packaging format.
</p>
<p>For example:</p>
<div class="code">
<pre>
&lt;entry xmlns="http://www.w3.org/2005/Atom"
xmlns:sword="http://purl.org/net/sword/"&gt;
&lt;title&gt;My Deposit&lt;/title&gt;
&lt;id&gt;info:something:1&lt;/id&gt;
&lt;updated&gt;2008-08-18T14:27:08Z&lt;/updated&gt;
&lt;author&gt;&lt;name&gt;jbloggs&lt;/name&gt;&lt;/author&gt;
&lt;summary type="text"&gt;A summary&lt;/summary&gt;
&lt;generator uri="http://www.appserver.org/engine" version="1.0"/&gt;
&lt;content type="application/zip"
src="http://www.appserver.org/col1/deposit1.zip"/&gt;
&lt;sword:packaging&gt;
http://purl.org/net/sword/package/METSDSpaceSIP
&lt;/sword:packaging&gt;
&lt;link rel="edit"
href="http://www.appserver.org/col1/my_deposit.atom" /&gt;
&lt;/entry&gt;
</pre>
</div>
<h2>4 Packaged Content Delivery over HTTP with AtomPub</h2>
<p>
A walkthrough of the process of delivering and retrieving packaged
content with a combination of the extensions described in this
specification and those detailed in [<a href="#sword001">SWORD001</a>].
</p>
<h3>4.1 Discovering Supported Packaging Formats for Delivery</h3>
<p>
The client requests the Service Document from the server, which
contains the <span class="code_inline">sword:mediation</span> and <span class="code_inline">sword:acceptPackaging</span> elements. If
the <span class="code_inline">sword:mediation</span> element is present and set to <span class="code_inline">true</span> this tells
the client that it can use the <span class="code_inline">On-Behalf-Of</span> HTTP header
[<a href="#sword001">SWORD001</a>] when delivering the packaged content. The
<span class="code_inline">sword:acceptPackaging</span> header tells the client what packaging
formats it can use to deliver that content.
</p>
<div class="code">
<pre>
&lt;service xmlns="http://www.w3.org/2007/app"
xmlns:sword="http://purl.org/net/sword/terms/"
xmlns:atom="http://www.w3.org/2005/Atom"&gt;
&lt;workspace&gt;
&lt;atom:title&gt;Main Site&lt;/atom:title&gt;
&lt;collection href="http://www.appserver.org/col1"&gt;
&lt;atom:title&gt;Collection 1&lt;/atom:title&gt;
&lt;accept&gt;application/zip&lt;/accept&gt;
&lt;sword:mediation&gt;true&lt;/sword:mediation&gt;
&lt;sword:acceptPackaging&gt;
http://purl.org/net/sword/package/BagIt
&lt;/sword:acceptPackaging&gt;
&lt;/collection&gt;
&lt;/workspace&gt;
&lt;/service&gt;
</pre>
</div>
<h3>4.2 Delivering Packaged Content</h3>
<p>
The client constructs a content package which meets the criteria
laid out in the <span class="code_inline">app:accept</span> and <span class="code_inline">sword:acceptPackaging</span> headers in the
Service Document; for example an application/zip BagIt packaged file.
This is delivered to the server as a standard POST of a Media
Resource:
</p>
<div class="code">
<pre>
POST /col1 HTTP/1.1
On-Behalf-Of: jbloggs
Packaging: http://purl.org/net/sword/package/BagIt
Content-Type: application/zip
</pre>
</div>
<p>The response to this MUST be as laid out in [<a href="#sword001">SWORD001</a>]</p>
<h3>4.3 Discovering Supported Package Formats for Retrieval</h3>
<p>
The supported formats for retrieval are listed in the Media Entry
document in the <span class="code_inline">sword:packaging</span> element. The client can retrieve
this document from the Media Entry URI, and discover the URI for the
content of the Media Resource and the supported package formats.
</p>
<div class="code">
<pre>
&lt;entry xmlns="http://www.w3.org/2005/Atom"
xmlns:sword="http://purl.org/net/sword/"&gt;
&lt;title&gt;My Deposit&lt;/title&gt;
&lt;id&gt;info:something:1&lt;/id&gt;
&lt;updated&gt;2008-08-18T14:27:08Z&lt;/updated&gt;
&lt;author&gt;&lt;name&gt;jbloggs&lt;/name&gt;&lt;/author&gt;
&lt;summary type="text"&gt;A summary&lt;/summary&gt;
&lt;generator uri="http://www.appserver.org/engine" version="1.0"/&gt;
&lt;content type="application/zip"
src="http://www.appserver.org/col1/deposit1.zip"/&gt;
&lt;sword:packaging&gt;
http://purl.org/net/sword/package/BagIt
&lt;/sword:packaging&gt;
&lt;sword:packaging&gt;
http://purl.org/net/sword/package/METSDSpaceSIP
&lt;/sword:packaging&gt;
&lt;link rel="edit"
href="http://www.appserver.org/col1/my_deposit.atom" /&gt;
&lt;/entry&gt;
</pre>
</div>
<p>
The presence of one or more <span class="code_inline">sword:packaging</span> elements tells the user
agent that it can request the Media Resource using the <span class="code_inline">Packaging</span> HTTP
header [<a href="#sword001">SWORD001</a>] to indicate its desired format.
</p>
<h3>4.4 Retrieving Packaged Content</h3>
<p>
The client issues an HTTP GET request on the Media Resource URI
and specifies the <span class="code_inline">Packaging</span> HTTP header [<a href="#sword001">SWORD001</a>], as follows:
</p>
<div class="code">
<pre>
GET /col1/deposit1.zip HTTP/1.1
Packaging: http://purl.org/net/sword/package/BagIt
</pre>
</div>
<p>
The server returns the Media Resource packaged as a BagIt zip file.
If the server does not support the requested format it MUST respond
as described in [<a href="#sword001">SWORD001</a>].
</p>
<h2>9 References </h2>
<h3>9.1 Normative References</h3>
<p>[<a name="rfc2119">RFC2119</a>] <a href="http://www.ietf.org/rfc/rfc2119.txt">S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.</a></p>
<p>[<a name="rfc2616">RFC2616</a>] <a href="http://www.ietf.org/rfc/rfc2616.txt">R. Fielding, UC Irvine, J. Gettys, J. Mogul, H. Frystyk, L. Masinter, P. Leach, T. Berners-Lee
"Hypertext Transfer Protocol -- HTTP/1.1",
RFC 2616, June 1999.</a></p>
<p>[<a name="rfc5023">RFC5023</a>] Gregorio, J. and B. de hOra, "The Atom Publishing
Protocol", RFC 5023, October 2007.</p>
<p>[<a name="sword001">SWORD001</a>] Jones, R, "Packaged Content Delivery over HTTP", Internet-
Draft, February 2011</p>
<h2>Copyright and License Notice</h2>
<p>
Copyright (C) SWORD (2011). All Rights Reserved.
</p>
<p>
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to SWORD, except as needed for the
purpose of developing Internet standards in which case the procedures
for copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
</p>
<p>
The limited permissions granted above are perpetual and will not be
revoked by SWORD or its successors or assigns.
</p>
This document and the information contained herein is provided on an
"AS IS" basis and SWORD DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
</p>
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