Semantic Web fundamentals: information linking and layering in practice

Or: what RDF might do for Drupal

The keynote session of DrupalCon day 4 is presented by Dan Brickley (@danbri) and is about Semantic Web. Dan Brickley is best known for his work on Web standards in the W3C community, where he helped create the Semantic Web project and many of its defining technologies.

His talk showed in practice how the full 1989 vision for the Web is being realised using RDF-based technologies (RDF/RDFa, SKOS, SPARQL, FOAF, OWL), and how the two concepts of information linking, and information layering are all you really need to understand a powerful suite of tools and standards for Web-based data sharing.

What is RDFa?

• A set of attributes for adding typed links and properties to document markup
• A bit like microformats, but with different strengths & weaknesses
• De-fragmenting the Web of Data?

Layered Information

Think of Calendars, Pixel Layers (Photoshop), Google Maps. All sort of layers helping you by adding information to data. We use this layering in Web Pages & databases already. Think of old-fashioned HTML hyperlinks, two identifiers referring to the same thing, etc.

Linked Data

Tim Berners-Lee: The Semantic Web isn't just about putting data on the web. It is about making links, so that a person or machine can explore the web of data. With linked data, when you have some of it, you can find other, related, data. Source

Thesauri and taxonomies

• Formal, logical taxonomies - OWL, Web Ontology Language
• Library-style thesauri, looser topical concept hierarchies - SKOS
• Examples of RDF results of Paris
  - http://rdf.freebase.com/rdf/en.paris
  - http://dbpedia.org/page/Paris

Search & RDF

• Yahoo SearchMonkey
• Google Rich Snippets

Files and workflow

• Adobe XMP
  Since 2001, RDF/XML inside TIFF, JPEG, PNG, GIF, PDF, etc)
• OpenOffice.org & OASIS OpenDocument Format 1.2
  Multifile archives, with a manifest and inline RDFa (Coming soon..)

RDFa in Drupal

• Uses DC (Dublin Core Metadata Initiative)
• Drupal Fields API is the core of it
• Attach arbitrary properties to anything in Drupal 7
• SKOS (a W3C standard) will brings dozens of thesauri, glossaries, etc
• Drupal code can call external SPARQL DBs (SPARQL is to RDF as SQL is to RDBs)

RDF/RDFa?

• RDF/XML is the oldest RDF syntax
• RDFa is a new, integrates with XHTML
• GRDDL lets you map from other XML or microformats

Summary

There's a growing ecosystem around linked RDF data.

Drupal can expect to manage files containing it, link to sites carrying it, and be populated with taxonomies expressed in it.