Modifying Queries on Complex Objects in Database Federations

We discuss the modification of queries against an integrated view in a federation of object-oriented databases. We present a generalization of existing algorithms for simple global query modification that works for arbitrarily defined integration classes. We then extend this algorithm to deal with object-oriented features that have been neglected in literature, viz. queries involving path expressions and nested queries. We show how properties of the OO-style of modeling relationships through object references can be exploited to reduce the number of subqueries necessary to evaluate such queries.