GRDDL Data Views: Getting Started, Learning More

GRDDL is a technique for gleaning resource descriptions from dialects of languages. It's a way of extracting Semantic Web data in RDF from XML formats (especially XHTML dialects or microformats) via transformations identified by URIs and typically expressed in XSLT. For full details, see the GRDDL specification.

Note: The GRDDL specification is a W3C Recommendation. W3C welcomes comments by email, especially comments that reflect implementation experience.

To use GRDDL:

If you're using a dialect (hDoap, Site Summaries, Embedded RDF, etc.) that already has an established GRDDL-compatible profile:
1. Add the profile attribute:
```
<html xmlns="http://www.w3.org/1999/xhtml">
  <head profile="http://purl.org/stuff/hdoap/profile">
    <title>My Project</title>
  </head>
    ...
</html>
```
2. Look at the data expressed as RDF using the online GRDDL demo service, and if you like, check its output with the W3C RDF Validation service, or with a tool more customized for your data, like the FOAF explorer.
3. Let the GRDDL Working Group know how you're using GRDDL by sending mail to the public-grddl-comments list.

If you're using an XHTML dialect (Dublin Core encoding, GeoURL markup, etc.) that has an existing transformation (dc-extract.xsl, grokGeoURL.xsl) ...

Make links from your XHTML data to the transformation, using the transformation link type:

<html xmlns="http://www.w3.org/1999/xhtml">
  <head profile="http://www.w3.org/2003/g/data-view">
    <title>Some Document</title>
    <link rel="transformation"
       href="http://www.w3.org/2000/06/dc-extract/dc-extract.xsl" />
    <meta name="DC.Subject"
       content="ADAM; Simple Search; Index+; prototype" />
    ...
  </head>
  ...
</html>

Reference the GRDDL profile to make it clear what that transformation link type means:

<html xmlns="http://www.w3.org/1999/xhtml">
  <head profile="http://www.w3.org/2003/g/data-view">
    <title>Some Document</title>
    ...

Check your data and let us know how it went as above.

Questions?

Q: How about more complete examples?
The GRDDL primer gives a number of examples in detail. Also, a home page for Joe Lambda shows DC, geoURL, RSS as above plus markup for FOAF (using grokFOAF.xsl) and Creative Commons Licenses (using grokCC.xsl) that you can probably figure out if you view source.
Q: Where can I find out about existing 'ways' rather than duplicate similar work?
A: The CustomRdfDialects wiki topic provides an informal directory of existing conventions.

If you just want to use GRDDL, that's all you need to know. If you're curious to learn more, read on...

GRDDL Namespace and Metadata Profile Reference

This document, http://www.w3.org/2003/g/data-view, is a metadata profile in the sense of the HTML specification, in section 7.4.4.3 Meta data profiles.

The following term is introduced here as an XHTML link relationship name and RDF property name:

transformation: relates a source document to a transformation, usually represented in XSLT, that relates the source document syntax to the RDF graph syntax. domain: RootNode; range: Transformation

The following terms are introduced here as RDF properties:

namespaceTransformation: relates a namespace to a transformation for all documents in that namespace. range: Transformation
profileTransformation: relates a profile document to a transformation for all documents bearing that profile. range: Transformation
result: an RDF graph obtained from an information resource by directly parsing a representation in the standard RDF/XML syntax or indirectly by parsing some other dialect using a transformation nominated by the document. domain: InformationResource; range: RDFGraph
transformationProperty relates a transformation to the algorithm specified by the property that computes an RDF graph from an XML document node domain: Transformation range: TransformationProperty
Transformation an InformationResource that specifies a transformation from a set of XML documents to RDF graphs Each Transformation has at least one transformationProperty that is a TransformationProperty.
TransformationProperty a FunctionalProperty that relates XML document root nodes to RDF graphs

The following terms are bound to concepts from existing standards:

RootNode the root of the tree in the XPath data model, per section 5.1 Root Node in XML Path Language (XPath) Version 1.0
RDFGraph a set of RDF triples, per definition in Resource Description Framework (RDF): Concepts and Abstract Syntax
InformationResource A resource which has the property that all of its essential characteristics can be conveyed in a message, per definition in Architecture of the World Wide Web, Volume One

We provide a sample GRDDL/XHTML implementation, and a more complete sample GRDDL implementation and a technical specification, Gleaning Resource Descriptions from Dialects of Languages (GRDDL), as a specification.

References

Acknowledgements and Colophon

This document uses Embedded RDF to encode Description of a Project (DOAP) data as well as RDF Schema data and one or two RDDL properties. We have moved away from the RDDL syntax itself.

This document was inspired by the XFN getting started page. Previous versions used XMDP (with grokXMDP.xsl), but in documenting domains and ranges of properties, maintaining the XMDP convention of ids on the dt rather than the dd element were too awkward to maintain.