Mixing Open and Closed World Assumption in Ontology-Based Data Access: Non-Uniform Data Complexity
When using ontologies to access instance data, it can be useful to make a Closed World Assumption (CWA) for some predicates and an Open World Assumption (OWA) for others. The main problem with such a setup is that Conjunctive Query (CQ) answering becomes intractable already for inexpressive description logics such as DL-Lite and EL. The authors take a closer look at this situation and carry out a fine-grained complexity analysis by considering the complexity of CQ answering w.r.t. individual TBoxes.