Rewriting Count Queries over DL-Lite TBoxes with Number Restrictions

We propose a query rewriting algorithm for a restricted class of conjunctive queries evaluated under count semantics over a DL-Lite knowledge base. The target query language is an extension of relational algebra with aggregation and arithmetic functions, which can be translated into SQL. The algorithm supports number restrictions on the RHS of axioms in the input TBox, which can be used to encode statistics. The size of the output query remains linear in the binary encoding of these numbers, which improves upon previously proposed approaches.