RDFex - Partial Imports of Common RDF Namespaces

September 23, 2009

Holger Knublauch <holger@topquadrant.com>

What is RDFex?

RDFex addresses a shortcoming of the OWL imports mechanism: owl:imports has an "all-or-nothing" philosophy, i.e. all triples from the target namespace are being added to the importing model. This often leads to models that are cluttered up with unnecessary definitions, making them more complex than necessary. In some cases, you may not even agree with the design assumptions made by the original ontology, but you still want to re-use the same identifiers. RDFex makes it possible to define subsets of common namespaces such as Dublin Core and makes them accessible with a short URI which can then be imported.


How does RDFex work?

Instead of the "official" URL for a namespace, you use a URL starting with http://rdfex.org/ followed by a prefix (see table below) and then a comma-separated list of those resource names that you wish to include from the target namespace. The server will return you an RDF/XML file that includes only the relevant subset of the original namespace, including type triples, labels and all relationships that lie within the partial ontology.

For example, assume you want to use parts of the FOAF namespace, but you are really only interested in the class foaf:Person and its property foaf:firstName. Using owl:imports <http://xmlns.com/foaf/0.1/> would bring in all of the FOAF namespace. Yet, in order to be a good Semantic Web citizen, you want to reuse the same identifiers in your own model.

In order to do a partial import of FOAF, use owl:imports <http://rdfex.org/foaf/Person,firstName>. (Click on the link to see the resulting RDF file.)


Which namespaces are supported by RDFex?

Currently, the following namespace prefixes are supported by RDFex. Please contact me if you would like to add other namespaces:

Prefix Namespace
dc http://purl.org/dc/elements/1.1/
dcterms http://purl.org/dc/terms/
foaf http://xmlns.com/foaf/0.1/
sioc http://rdfs.org/sioc/ns
skos http://www.w3.org/2004/02/skos/core


Who is behind RDFex?

RDFex is provided as a free web service by TopQuadrant. The server software is TopBraid Live on Apache Tomcat.