Title : From Logical Query Rewriting to Plan Selection for Ontology-Based Query Answering
Abstract: The last decade has seen a lot of research effort on ontology based query answering, which is the problem of querying data using the terms of an ontology. This is a key functionality in the seamless semantic interrogation of a knowledge base. A popular approach towards practical algorithms is the so-called rewriting approach, where the original query is rewritten using the ontology. The ontology can then be discarded, and the rewriting directly evaluated on the underlying database.
In this talk, we will present the two main challenges inherent to this approach. First, the computation of the logical rewriting is complex. We will provide the key ideas behind the main algorithms. Second, the rewritten queries are of a form for which traditional database systems have not been optimized for: this raises new challenges for query optimization, which need to be solved to get practical semantic querying.