One of the most important reasoning tasks on queries is checking containment, ie, verifying
whether one query yields necessarily a subset of the result of another one. Query
containment is crucial in several contexts, such as query optimization, query reformulation,
knowledge-base verification, information integration, integrity checking, and cooperative
answering. Containment is undecidable in general for Datalog, the fundamental language
for expressing recursive queries. On the other hand, it is known that containment between …

One of the most important reasoning tasks on queries is checking containment, ie, verifying
whether one query yields necessarily a subset of the result of another one. Query
containment, is crucial in several contexts, such as query optimization, query reformulation,
knowledge-base verification, information integration, integrity checking, and cooperative
answering. Containment is undecidable in general for Datalog, the fundamental language
for expressing recursive queries. On the other hand, it is known that containment between …