We discuss 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.