RDF in Drupal 7 and the Web at large

(notes on a session at DrupalCon 2010)

Lin Clark of DERI Galway, heavy D7 contributor

RDF is based on very basic principles
programs and sites can exchange information
search engines can display more relevant info in results because of structured data
data mashers can combine different datasets to reveal new things
"machine understandable": information explicitly marked up by what it means rather than relying on context
RDF = Resource Description Framework
- a resource is a uniquely named thing. rather than providing a full URI, can provide a namespace and build a CURIE (compact URI) from that namespace.
- a resource can also have a type, defined by another CURIE.
- relationships among resources can also have types defined in CURIEs.
"Giant Clobal Graph" = what the Web will become when everyone uses RDF
SPARQL is query language for retrieving RDF information
Drupal has internal structure similar to RDF, but in the past it hasn't been marked up externally in the HTML.
Drupal's field names have been idiosyncratic in the past; RDF will make them universally dereferenceable.

History of RDF in Drupal

Dries wrote an rdf.php for Drupal back in 2000
RDF module written in 2007, RDF CCK in 2008
RDF is serialized as RDFa so it can be embedded in other XML files. (a = attributes)
RDFa is standardized in XHTML 1.1 and HTML 5.
use the property, typeof, rel attributes of HTML tags to assign RDF properties to data
RDF is credited with a 30% increase in search traffic, instantly improves search results

How to use it in D7

Drupal is pioneering RDFa adoption
all core entity types are marked up with RDF attributes: title, date, fields, comment count, reply to, creator.
all core entities have "cool URIs": node/#, comment/#, user/#, taxonomy/term/#
support FOAF (people), SIOC (authorship), SKOS (terms), DC (generic properties) vocabulary namespaces out of the box.
use page caching to avoid performance hit, especially on pages with lots of comments.

What's coming up

There will be a mapping user interface for D7 - not yet complete.
There will also be a SPARQL endpoint, so anyone will be able to query site's data
RDF proxy will allow for automatic updating of remote data when source is changed.

RDF in D7 for developers

Interdependent Web