View source for Tracker CC Indexing

[[Category:Technology]]
[[Category:Developer]]
[[Category:metadata]]
[[Category:Tracker]]

== Google Summer of Code Project: “Indexing Embedded License Claims in Tracker” ==

Here's some relevant (now revised) sections of the Summer of Code application:

== License Metadata Summary ==

<table border="1">
<tr>
<td><strong>Format</strong></td><td><strong>Form of Metadata</strong></td><td><strong>Location of Metadata</strong></td><td><strong>Links</strong></td>
</tr>
<tr><td colspan="4"><strong>Audio</strong></td></tr>
<tr>
  <td>MP3</td>
  <td>XMP / Native id3 tags</td>
  <td>The PRIV,XMP field / WCOP tag</td>
  <td>[http://partners.adobe.com/public/developer/en/xmp/sdk/XMPspecification.pdf XMP Spec]
[http://www.id3.org/id3v2.3.0 ID3v2.3 Spec]</td>
</tr>
<tr>
  <td>Vorbis</td>
  <td>XMP / Native comment field</td>
  <td>XMP comment field / LICENSE comment field</td>
  <td>[http://xiph.org/vorbis/doc/v-comment.html Ogg Vorbis Docs]</td>
</tr>
<tr>
  <td>FLAC</td>
  <td>Native comment fields (id3v2 or vorbis-style comments)</td>
  <td>Same as with MP3 for id3v2 or Vorbis for vorbis-style comments</td>
  <td>[http://flac.sourceforge.net/format.html#metadata_block_vorbis_comment FLAC Format Spec]</td>
</tr>
<tr>
  <td>Monkey's Audio (APE)</td>
  <td>Native Vorbis-like comment field</td>
  <td>AFAIK, there is no standard tag spec</td>
  <td></td>
</tr>
<tr><td colspan="4"><strong>Images</strong></td></tr>
<tr>
  <td>JPEG</td>
  <td>XMP</td>
  <td>APP1 Markers</td>
  <td>[http://partners.adobe.com/public/developer/en/xmp/sdk/XMPspecification.pdf XMP Spec]</td>
</tr>
<tr>
  <td>JPEG 2000</td>
  <td>XMP</td>
  <td>UUID Box</td>
  <td>[http://partners.adobe.com/public/developer/en/xmp/sdk/XMPspecification.pdf XMP Spec]</td>
</tr>
<tr>
  <td>TIFF</td>
  <td>XMP</td>
  <td>XMLPacket tag</td>
  <td>[http://partners.adobe.com/public/developer/en/xmp/sdk/XMPspecification.pdf XMP Spec]</td>
</tr>
<tr>
  <td>PNG</td>
  <td>XMP</td>
  <td>iTXt, XML:com:adobe:xmp field</td>
  <td>[http://partners.adobe.com/public/developer/en/xmp/sdk/XMPspecification.pdf XMP Spec]</td>
</tr>
<tr>
  <td>GIF</td>
  <td>XMP</td>
  <td>Application block</td>
  <td>[http://partners.adobe.com/public/developer/en/xmp/sdk/XMPspecification.pdf XMP Spec]</td>
</tr>
<tr>
  <td>SVG</td>
  <td>RDF</td>
  <td>/svg/metadata/rdf</td>
  <td>[http://wiki.creativecommons.org/SVG CC Wiki, SVG, based on Inkscape]</td>
</tr>
<tr>
  <td>PSD (Adobe Photoshop)</td>
  <td>XMP</td>
  <td>Resource block</td>
  <td>[http://partners.adobe.com/public/developer/en/xmp/sdk/XMPspecification.pdf XMP Spec]</td>
</tr>
<tr><td colspan="4"><strong>Video</strong></td></tr>
<tr>
  <td>AVI</td>
  <td>?</td>
  <td>?</td>
  <td>[http://partners.adobe.com/public/developer/en/xmp/sdk/XMPspecification.pdf XMP Spec]</td>
</tr>
<tr>
  <td>Matroska</td>
  <td>Native tag</td>
  <td>COPYRIGHT tag</td>
  <td>[http://www.matroska.org/technical/specs/tagging/index.html Matroska Tagging Spec]</td>
</tr>
<tr>
  <td>Quicktime</td>
  <td>Native tag</td>
  <td>kMDItemCopyright(old)/kUserDataTextCopyright(new) tag</td>
  <td>[http://developer.apple.com/documentation/QuickTime/Conceptual/QT7UpdateGuide/Chapter03/chapter_3_section_1.html#//apple_ref/doc/uid/TP40001163-CH314-553378 Quicktime 7 API Reference]
[http://partners.adobe.com/public/developer/en/xmp/sdk/XMPspecification.pdf XMP Spec]</td>
</tr>
<tr>
  <td>OGG</td>
  <td>No metadata standard</td>
  <td></td>
  <td>[http://wiki.xiph.org/Metadata Ogg Metadata Draft]</td>
</tr>
<tr>
  <td>Theora</td>
  <td colspan="2">Theora comments (similar to Vorbis comments)</td>
  <td>[http://www.theora.org/doc/Theora_I_spec.pdf Theora Spec]</td>
</tr>
<tr>
  <td>Flash</td>
  <td>RDF</td>
  <td>?</td>
  <td></td>
</tr>
<tr><td colspan="4"><strong>Documents</strong></td></tr>
<tr>
  <td>PDF</td>
  <td>XMP</td>
  <td>metadata field</td>
  <td>[http://partners.adobe.com/public/developer/en/xmp/sdk/XMPspecification.pdf XMP Spec]</td>
</tr>
<tr>
  <td>Postscript/EPS</td>
  <td>XMP</td>
  <td>Document-level metadata</td>
  <td>[http://partners.adobe.com/public/developer/en/xmp/sdk/XMPspecification.pdf XMP Spec]</td>
</tr>
<tr>
  <td>HTML</td>
  <td>RDFa</td>
  <td>&lt;a rel="license" href="..."&gt;&lt;/a&gt;</td>
  <td>[http://wiki.creativecommons.org/RDFa CC Wiki, RDFa]</td>
</tr>
<tr>
  <td>SMIL</td>
  <td>RDF</td>
  <td>/smil/head/metadata@id="meta-rdf"/RDF</td>
  <td>[http://web.resource.org/cc/modules/smil/ CreativeCommons SMIL Module]</td>
</tr>
<tr>
  <td>RSS 1.0</td>
  <td colspan="2">/RDF/channel/license or /RDF/channel/item/license</td>
  <td>[http://web.resource.org/rss/1.0/modules/cc/ CreativeCommons RSS 1.0 Module]</td>
</tr>
<tr>
  <td>RSS 2.0</td>
  <td colspan="2">/rss/channel/cc:license or /rss/channel/item/cc:license</td>
  <td>[http://backend.userland.com/creativeCommonsRssModule CreativeCommons RSS 2.0 Module]</td>
</tr>
<tr>
  <td>Atom</td>
  <td colspan="2">/feed/entry/link@rel=license</td>
  <td>[http://ietfreport.isoc.org/idref/draft-snell-atompub-feed-license/ Atom License Extension]</td>
</tr>
<tr>
  <td>Any XML</td>
  <td>XMP</td>
  <td>Wherever valid</td>
  <td>[http://partners.adobe.com/public/developer/en/xmp/sdk/XMPspecification.pdf XMP Spec]</td>
</tr>
<tr>
  <td>OpenOffice.org (OASIS)</td>
  <td colspan="2">OO.org CC License Add-In SoC Project is working on the spec</td>
  <td></td>
</tr>
<tr>
  <td>MS Office (2003)</td>
  <td>DocumentSummaryInformation Infile</td>
  <td>CreativeCommons_LicenseURL property</td>
  <td>[http://www.microsoft.com/downloads/details.aspx?FamilyID=113b53dd-1cc0-4fbe-9e1d-b91d07c76504&displaylang=en Office Add-in]</td>
</tr>
<tr>
  <td>MS Office OpenXML (2007)</td>
  <td>?</td>
  <td>?</td>
  <td>[http://www.ecma-international.org/publications/standards/Ecma-376.htm OpenXML Spec]

[http://lists.ibiblio.org/pipermail/cc-devel/2007-June/000466.html Relevant mailing list post]</td>
</tr>

</table>

== Indexing Licenses in Tracker Summary ==

<table border="1">
<tr>
<td><strong>Status</strong></td><td><strong>Format</strong></td><td><strong>Extraction Method</strong></td><td><strong>Test content</strong></td>
</tr>
<tr>
  <td>Done, GStreamer patch pending</td>
  <td>MP3</td>
  <td>Reading native tags already complete.  Maybe extend GStreamer extractor to read XMP.</td>
  <td>XMP embedded with Exempi / Tags embedded with id3v2</td>
</tr>
<tr>
  <td>In progress</td>
  <td>Vorbis</td>
  <td>Extend the GStreamer extractor to check for the presence of an XMP comment field.  GStreamer places this within the EXTENDED_COMMENTS tag (requires GStreamer 0.10.10).</td>
  <td>XMP embedded with vorbiscomment</td>
</tr>
<tr>
  <td>Done, GStreamer patch pending</td>
  <td>FLAC</td>
  <td>Native tags already extracted through the GStreamer extractor.  Maybe extend GStreamer extractor to read XMP.</td>
  <td>embedded with id3v2 or metaflac</td>
</tr>
<tr>
  <td>In progress</td>
  <td>JPEG</td>
  <td>Extend the Imagemagick extractor, using 'convert file.jpg xmp:-' to read XMP</td>
  <td>XMP embedded with Exempi</td>
</tr>
<tr>
  <td>Patch pending</td>
  <td>TIFF</td>
  <td>Extend the Imagemagick extractor, using 'convert file.tif xmp:-' to read XMP</td>
  <td>XMP embedded with Exempi (Note: there's a bug in Adobe's XMP SDK that prevents Exempi from embedding valid XMP)</td>
</tr>
<tr>
  <td>Pending release of libpng-1.3/Pending Tracker patch</td>
  <td>PNG</td>
  <td>Extend the PNG extractor, adding a check for XML:com:adobe:xmp.  (For backwards compatibility, the ability to read iTXt in libpng is disabled by default until version 1.3.)</td>
  <td>XMP embedded with Exempi</td>
</tr>
<tr>
  <td>In progress</td>
  <td>GIF</td>
  <td>Would need to write a GIF extractor</td>
  <td>Palimpsest</td>
</tr>
<tr>
  <td>Poppler patch accepted, Tracker patch pending</td>
  <td>PDF</td>
  <td>Extend the current PDF extractor (which uses Poppler) to read the metadata field.</td>
  <td>XMP embedded with Exempi</td>
</tr>
<tr>
  <td>Patch pending</td>
  <td>HTML</td>
  <td>Write a new HTML extractor, using libxml2, and scan for RDFa</td>
  <td>Various actual sites, including creativecommons.org</td>
</tr>
<tr>
  <td>In progress</td>
  <td>SVG</td>
  <td>I could specifically parse the XML, checking for the RDF schema used by Inkscape.  Should I check for XMP also???</td>
  <td>Inkscape</td>
</tr>
<tr>
  <td></td>
  <td>Any XML</td>
  <td>Write a generic XML extractor (and/or extractor for each particular format), scanning with libxml2</td>
  <td></td>
</tr>
<tr>
  <td>Awaiting spec</td>
  <td>OpenOffice.org (OASIS)</td>
  <td>Extend OASIS extractor</td>
  <td>OO.org Add-In</td>
</tr>
<tr>
  <td>Patch pending</td>
  <td>MS Office</td>
  <td>Extend existing msoffice extractor</td>
  <td>[http://www.microsoft.com/downloads/details.aspx?FamilyID=113b53dd-1cc0-4fbe-9e1d-b91d07c76504&amp;displaylang=en MSOffice Add-in]</td>
</tr>
</table>

== Timeline ==

UPDATE:  It's going to be difficult to estimate progress of when I'll do what.  Patches are being sent upstream of various dependencies of Tracker.  Completion of indexing of particular formats varies as I await approval of patches and feedback from upstream, as well as Jamie's approval of patches into Tracker itself.  I'll be working on various aspects of the project in parallel as I await feedback/approval on a particular aspect.

Check out the above table of progress for where I'm at with what.

By week 12: Tie things up for submission of code

== Implementation ==

XMP

The following is an excerpt of raw XMP describing a work licensed under the CC Attribution 3.0 license.

<pre>
<?xpacket begin='' id=''?><x:xmpmeta xmlns:x='adobe:ns:meta/'>
<rdf:RDF xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>

 <rdf:Description rdf:about=''
  xmlns:xapRights='http://ns.adobe.com/xap/1.0/rights/'>
  <xapRights:Marked>True</xapRights:Marked>
 </rdf:Description>

 <rdf:Description rdf:about=''
  xmlns:dc='http://purl.org/dc/elements/1.1/'>
  <dc:rights>
   <rdf:Alt>
    <rdf:li xml:lang='x-default' >This work is licensed under a Creative Commons
 Attribution 3.0  License.</rdf:li>
   </rdf:Alt>
  </dc:rights>
 </rdf:Description>

 <rdf:Description rdf:about=''
  xmlns:cc='http://creativecommons.org/ns#'>
  <cc:license rdf:resource='http://creativecommons.org/licenses/by/3.0/'/>
 </rdf:Description>

</rdf:RDF>
</x:xmpmeta>
<?xpacket end='r'?>
</pre>

To fit Tracker's metadata structure, the extracted license claim would be placed into the File:License field in a form such as: "This work is licensed under a Creative Commons Attribution 3.0 License (http://creativecommons.org/licenses/by/3.0/)". Such a format allows for searching the license field by both license name and URL.

Specifically,

 /rdf:Description[@xmlns:dc='http://purl.org/dc/elements/1.1/']/dc:rights/rdf:Alt/rdf:li/text()

and

 /rdf:Description[@xmlns:cc='http://creativecommons.org/ns#']/cc:license/attribute:rdf:resource

Will be stored in Tracker's File:License field.

== Links ==

* Related works
** cclookup (http://wiki.creativecommons.org/CcLookup) - Python application for extracting license RDF metadata or license metadata from mp3s. Code may be adapted for parsing license claims in C
** ccpublisher (http://wiki.creativecommons.org/CcPublisher) - Licenses embedded by ccpublisher should all be correctly extracted.
* Related links
** http://creativecommons.org/technology/usingmarkup
** http://wiki.creativecommons.org/RDFa