Query Rewriting Using Views in a Typed Mediator Environment

Query rewriting method is proposed for the heterogeneous information integration infrastructure formed by the subject mediator environment. Local as View (LAV) approach treating schemas exported by sources as materialized views over virtual classes of the mediator is considered as the basis for the subject mediation infrastructure. In spite of significant progress of query rewriting with views, it remains unclear how to rewrite queries in the typed, objectoriented mediator environment. This paper embeds conjunctive views and queries into an advanced canonical object model of the mediator. The “selectionprojection-join” (SPJ) conjunctive query semantics based on type specification calculus is introduced. The paper demonstrates how the existing query rewriting approaches can be extended to be applicable in such typed environment. The paper shows that refinement of the mediator class instance types by the source class instance types is the basic relationship required for establishing query containment in the object environment.