SoftFacts: a top-k retrieval engine for ontology mediated access to relational databases

We outline SoftFacts, an ontology mediated top-k information retrieval system over relational databases. An ontology layer is used to define (in terms of a OWL-QL like Semantic Web language) the relevant abstract concepts and relations of the application domain, while graded facts are stored into a relational database. Queries are conjunctive queries with ranking aggregates and scoring functions and the results of a query may be ranked according to user defined scoring functions. We will illustrate SoftFacts' architecture, the representation and the query language, sketch the reasoning algorithms of the SoftFacts~system and its Protege plug-in.