GRDDL (pronounced "''griddle''") is a markup format for Gleaning Resource Descriptions from Dialects of Languages. It is a
W3C Recommendation
The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web. Founded in 1994 by Tim Berners-Lee, the consortium is made up of member organizations that maintain full-time staff working together in ...
XML
Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing data. It defines a set of rules for encoding electronic document, documents in a format that is both human-readable and Machine-r ...
documents, including
XHTML
Extensible HyperText Markup Language (XHTML) is part of the family of XML markup languages which mirrors or extends versions of the widely used HyperText Markup Language (HTML), the language in which Web pages are formulated.
While HTML, pr ...
. The GRDDL specification shows examples using
XSLT
XSLT (Extensible Stylesheet Language Transformations) is a language originally designed for transforming XML documents into other XML documents, or other formats such as HTML for web pages, plain text, or XSL Formatting Objects. These formats c ...
A document specifies associated transformations, using one of a number of ways.
For instance, an XHTML document may contain the following markup:
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:
This code is valid for
XHTML
Extensible HyperText Markup Language (XHTML) is part of the family of XML markup languages which mirrors or extends versions of the widely used HyperText Markup Language (HTML), the language in which Web pages are formulated.
While HTML, pr ...
1.x only. The profile attribute has been dropped in
HTML5
HTML5 (Hypertext Markup Language 5) is a markup language used for structuring and presenting hypertext documents on the World Wide Web. It was the fifth and final major HTML version that is now a retired World Wide Web Consortium (W3C) recommend ...
, including its XML serialisation.
Microformats and profile transformations
If an XHTML page contains Microformats, there is usually a specific profile.
For instance, a document with hcard information should have:
When fetched http://www.w3.org/2006/03/hcard has:
and
The GRDDL aware agent can then use that profileTransformation to extract all hcard data from pages that reference that link.
XML and transformations
In a similar fashion to XHTML, GRDDL transformations can be attached to XML documents.
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
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 minimal effort from the namespace author.
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.
Implementations
GRDDL consumers (also known as GRDDL aware agents)
Microformats
Microformats (μF) are predefined HTML markup (like HTML classes) created to serve as descriptive and consistent metadata about HTML element, elements, designating them as representing a certain type of data (such as address book, contact info ...
– a simplified approach to semantically annotate data in websites
* RDFa – a
W3C
The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web. Founded in 1994 by Tim Berners-Lee, the consortium is made up of member organizations that maintain full-time staff working together in ...
Recommendation for annotating websites with RDF data