19. Functional Queries to Wrapped Educational Semantic Web Meta-Data

The aim of the Edutella project is to provide a peer-to-peer infras- tructure for educational material retrieval using semantic web meta-data descriptions of educational resources. Edutella uses the semantic web meta-data description languages RDF and RDF-Schema for describing web resources. The aim of this work is to wrap the Edutella infrastruc- ture with a functional mediator system. This makes it possible to define general functional queries and views over educational and other material described using RDF and RDF-Schema. It is based on the observation that RDF-Schema definitions are easily mapped into a functional data model. This allows any RDF-Schema file to be wrapped by a functional mediator system. The RDF-Schema definitions are translated into a cor- responding functional meta-data schema consisting of a type hierarchy and a set of functions. Queries then can be expressed in terms of the translated semantic functional schema. Since meta-data descriptions can contain both RDF and RDF-Schema definitions the system allows both to co-exist with the difference that queries over basic RDF meta-data are expressed on a lower level in terms of a generic functional schema repre- senting all RDF structures.