Exact Query Reformulation over SHOQ DBoxes

We formalise the problem of query reformulation over a description logic ontology and a DBox in a general framework. This framework supports deciding the existence of a safe-range first-order equivalent reformulation of a concept query in terms of the signature of a DBox. A constructive method to compute the reformulation is provided. We are particularly interested in safe-range reformulations since they can be transformed to relational queries and executed using SQL. We also discuss the completeness of the proposed framework with respect to finite and unrestricted models. As a case study we consider ontologies and queries expressed in SHOQ.