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.

How it works Edit

XHTML & Transformations Edit

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

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

   <head profile="">

   <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:

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

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

Microformats & Profile Transformations Edit

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

For instance, a document with hcard information should have:

<head profile="">

When fetched has:

<head profile="">


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

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

XML & Transformations Edit

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

XML Namespace Transformations Edit

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="">
   <!-- document content here -->

and when fetched, 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.

Output Edit

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.


GRDDL Consumers (also known as GRDDL Aware Agents)Edit

See also Edit

  • 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

External links Edit


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