Bending the rules without breaking the repo: Using free RDF description in Fedora Commons repositories

Fedora Commons has for many years distinguished itself in the field of repository frameworks by its expansive use of RDF for content modeling and description. 
	⁃	Its Content Modeling Architecture assembles a simple type system for content by use of RDF assertions.
	⁃	Administrative and structural metadata, by default, is indexed in an RDF triplestore and made available via SPARQL endpoint.
	⁃	Community praxis has supported the construction of fine-grained object graphs for content modeling via RDF relationships. 
Many integrators and developers rely on these features to create production services.

But Fedora's abilities to manage and index RDF is very limited. In particular, it cannot permit of the use of RDF triple with subjects that are not Fedora-curated resources (objects or datastreams). This makes impossible the use of richly-textured descriptions, for example in the style of Dublin Core in RDF. Additionally, RDF associated to an individual object must be stored in one of two special-purpose datastreams with constrained semantics (RELS-EXT and RELS-INT). This means that any metadata assertions that should be available as RDF must be stored as RDF/XML. If the authoritative version of the metadata in question is not RDF/XML, this necessitates the creation and maintenance of workflow machinery external to the repository.

This poster will present the design and use of an experimental extension module for Fedora that ameliorates some of these problems. It permits the management, in the Fedora Resource Index triplestore, of RDF assertions drawn from arbitrary XML metadata streams in an object. It allows for the creation and management of RDF triples the subjects of which are not Fedora resources, including (via automatic Skolemization) enabling the functionality of blank nodes without their actual appearance. And it does these things with nothing more than simple XML configuration and XSLT stylesheets that dynamically transform XML metadata to RDF/XML as an automatic part of repository operation.

The software is available now at:

https://github.com/ajs6f/fcrepo-xslt-triplegenerator

and its rationale and basic instructions for installing and configuring it are available at:

http://ajs6f.github.com/fcrepo-xslt-triplegenerator/

This poster will be accompanied by live demonstration of the use of this software to maintain rich RDF descriptions of Fedora objects using Dublin Core XML and MODS XML as the authoritative and only sources of metadata, without external workflow apparatus. The appearance of complete RDF graphs for these descriptions at Fedora's SPARQL endpoint will be a particular feature of the demonstration.