XML::GRDDL(3) 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# <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.

AUTHOR

Toby Inkster <[email protected]>.

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.

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