Toby Inkster

NAME

XML::GRDDL - transform XML and XHTML to RDF

SYNOPSIS

High-level interface:

 my $grddl = XML::GRDDL->new;
 my $model = $grddl->data($xmldoc, $baseuri);
 # $model is an RDF::Trine::Model

Low-level interface:

 my $grddl = XML::GRDDL->new;
 my @transformations = $grddl->discover($xmldoc, $baseuri);
 foreach my $t (@transformations)
 {
   # $t is an XML::GRDDL::Transformation
   my ($output, $mediatype) = $t->transform($xmldoc);
   # $output is a string of type $mediatype.
 }

DESCRIPTION

GRDDL is a W3C Recommendation for extracting RDF data from arbitrary XML and XHTML via a transformation, typically written in XSLT. See http://www.w3.org/TR/grddl/ for more details.

This module implements GRDDL in Perl. It offers both a low level interface, allowing you to generate a list of transformations associated with the document being processed, and thus the ability to selectively run the transformation; and a high-level interface where a single RDF model is returned representing the union of the RDF graphs generated by applying all available transformations.

Constructor

XML::GRDDL->new

The constructor accepts no parameters and returns an XML::GRDDL object.

Methods

$grddl->discover($xml, $base, %options)

Processes the document to discover the transformations associated with it. $xml is the raw XML source of the document, or an XML::LibXML::Document object. ($xml cannot be "tag soup" HTML, though you should be able to use HTML::HTML5::Parser to parse tag soup into an XML::LibXML::Document.) $base is the base URI for resolving relative references.

Returns a list of XML::GRDDL::Transformation objects.

Options include:

  • force_rel - boolean; interpret XHTML rel="transformation" even in the absence of the GRDDL profile.

  • strings - boolean; return a list of plain strings instead of blessed objects.

$grddl->data($xml, $base, %options)

Processes the document, discovers the transformations associated with it, applies the transformations and merges the results into a single RDF model. $xml and $base are as per discover.

Returns an RDF::Trine::Model containing the data. Statement contexts (a.k.a. named graphs / quads) are used to distinguish between data from the result of each transformation.

Options include:

  • force_rel - boolean; interpret XHTML rel="transformation" even in the absence of the GRDDL profile.

  • metadata - boolean; include provenance information in the default graph (a.k.a. nil context).

$grddl->ua( [$ua] )

Get/set the user agent used for HTTP requests. $ua, if supplied, must be an LWP::UserAgent.

Constants

These constants may be exported upon request.

GRDDL_NS
XHTML_NS

FEATURES

XML::GRDDL supports transformations written in XSLT 1.0, and in RDF-EASE.

XML::GRDDL is a good HTTP citizen: Referer headers are included in requests, and appropriate Accept headers supplied. To be an even better citizen, I recommend changing the User-Agent header to advertise the name of the application:

 $grddl->ua->default_header(user_agent => 'MyApp/1.0 ');

Provenance information for GRDDL transformations is returned using the GRDDL vocabulary at http://www.w3.org/2003/g/data-view#.

Certain XHTML profiles and XML namespaces known not to contain any transformations, or to contain useless transformations are skipped. See XML::GRDDL::Namespace and XML::GRDDL::Profile for details. In particular profiles for RDFa and many Microformats are skipped, as RDF::RDFa::Parser and HTML::Microformats will typically yield far superior results.

BUGS

Please report any bugs to http://rt.cpan.org/.

Known limitations:

  • Recursive GRDDL doesn't work yet.

    That is, the profile documents and namespace documents linked to from your primary document cannot themselves rely on GRDDL.

SEE ALSO

XML::GRDDL::Transformation, XML::GRDDL::Namespace, XML::GRDDL::Profile, XML::GRDDL::Transformation::RDF_EASE::Functional, XML::Saxon::XSLT2.

HTML::HTML5::Parser, RDF::RDFa::Parser, HTML::Microformats.

JSON::GRDDL.

http://www.w3.org/TR/grddl/.

http://www.perlrdf.org/.

This module is derived from Swignition http://buzzword.org.uk/swignition/.

AUTHOR

Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE

Copyright 2008-2012 Toby Inkster

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

DISCLAIMER OF WARRANTIES

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.