Department of Computer and Information Science
University of Pennsylvania
4pm Tuesday 8 Juli 2003
Room 3218, JCMB, King's Buildings
For the relational data model there exists a rich and interesting theory of conjunctive queries and of the containment-expressing dependencies corresponding to them. Query containment and minimization, plain or under dependencies, was studied during the classical times of relational database theory (1975-1985). Relational query reformulation, specifically rewriting with views, was studied more recently. A lot of interest in a similar theory for the XML data model is now emerging and this talk presents an attempt to contribute to such a theory.
Our strategy is to solve XML "conjunctive" query containment and reformulation problems via sound and complete reductions to relational problems that can be solved with the chase technique and with our Chase&Backchase algorithm (joint with Lucian Popa, IBM Almaden) for query minimization under dependencies.
Joint work with Alin Deutsch, UC San Diego.