GRDDL (pronounced 'griddle') is a markup format for Gleaning Resource Descriptions from Dialects of Languages.
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="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:
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="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:
<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.
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="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.
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
- OpenLink Virtuoso through its Sponger cartridge system
- XML_GRDDL, a semi compliant PHP 5 library
- See other implementations
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
- W3C GRDDL Specification
- W3C GRDDL Working Group
- W3C GRDDL Primer
- W3C GRDDL Use-Cases
- GRDDL Quick Reference (pdf)