Optimizing Query Answering under Ontological Constraints
Ontological queries are evaluated against a database combined with ontological constraints. Answering such queries is a challenging new problem for database research. For many ontological modeling languages, query answering can be solved via query rewriting: given a conjunctive query and ontology, the query can be transformed into a first-order query, called the perfect rewriting, that takes into account the semantic consequences of the ontology. Then, for every extensional database D, the answer to the query is obtained by evaluating the rewritten query against D.