GRDDL

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GRDDL (pronounced 'griddle') is a markup format for Gleaning Resource Descriptions from Dialects of Languages.

It is a W3C Recommendation, and enables users to get RDF out of XML and XHTML documents via XSLT.

It became a recommendation on September 11, 2007.


Contents

[edit] How it works

[edit] XHTML & Transformations

A document specifies associated transformations, using one of a number of ways.

For instance, an XHTML document may contain the following markup:

   <head profile="http://www.w3.org/2003/g/data-view
                http://dublincore.org/documents/dcq-html/
                http://gmpg.org/xfn/11">

   <link rel="transformation" href="grokXFN.xsl" />

Document consumers are informed that there are GRDDL transformations available in this page, by including the following in the PROFILE attribute of the HEAD element:

   http://www.w3.org/2003/g/data-view

The available transformations are revealed through one or more LINK elements:

   <link rel="transformation" href="grokXFN.xsl" />

[edit] Microformats & Profile Transformations

If an XHTML page contains Microformats, there is usually a specific profile.

For instance, a document with hcard information should have:

<head profile="http://www.w3.org/2003/g/data-view http://www.w3.org/2006/03/hcard">

When fetched http://www.w3.org/2006/03/hcard has:

<head profile="http://www.w3.org/2003/g/data-view">

and

<p>Use of this profile licenses RDF data extracted by 
   <a rel="profileTransformation" href="../vcard/hcard2rdf.xsl">hcard2rdf.xsl</a>
    from <a href="http://www.w3.org/2006/vcard/ns">the 2006 vCard/RDF work</a>.
</p>

The GRDDL aware agent can then use that profileTransformation to extract all hcard data from pages that reference that link.


[edit] XML & Transformations

In a similar fashion to XHTML, GRDDL transformations can be attached to XML documents.

[edit] XML Namespace Transformations

Just like a profileTransformation, an XML namespace can have a transformation associated with it.

This allows entire XML dialects (for instance, KML or Atom) to provide meaningful RDF.

An XML document simply points to a namespace

<foo xmlns="http://example.com/1.0/">
   <!-- document content here -->
</foo>

and when fetched, http://example.com/1.0/ points to a namespaceTransformation.

This also allows very large amounts of the existing XML data in the wild to become RDF/XML with a very minimal effort from the namespace author.

[edit] Output

Once a document has been transformed, there is an RDF representation of that data.

This output is generally put into a database and queried via SPARQL.

[edit] Implementations

[edit] GRDDL Consumers (also known as GRDDL Aware Agents)

[edit] See also

  • microformats, a simplified approach to semantically annotate data in websites
  • RDFa, a W3C proposal for annotating websites with RDF data
  • eRDF, an alternative to RDFa

[edit] External links

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