Top-k retrieval for ontology mediated access to relational databases

We address the problem of evaluating ranked top-k queries in the context of ontology mediated access over relational databases. An ontology layer is used to define the relevant abstract concepts and relations of the application domain, while facts with associated score are stored into a relational database. Queries are conjunctive queries with ranking aggregates and scoring functions. The results of a query may be ranked according to the score and the problem is to find efficiently the top-k ranked query answers.