Implementing mapping composition
Mapping composition is a fundamental operation in metadata driven applications. Given a mapping over schemas sigma(1) and sigma(2) and a mapping over schemas sigma(2) and sigma(3), the composition problem is to compute an equivalent mapping over or, and sigma(3). We describe a new composition algorithm that targets practical applications. It incorporates view unfolding. It eliminates as many sigma(2) symbols as possible, even if not all can be eliminated. It covers constraints expressed using arbitrary monotone relational operators and, to a lesser extent, non-monotone operators. And it introduces the new technique of left composition. We describe our implementation, explain how to extend it to support user-defined operators, and present experimental results which validate its effectiveness.
mapping composition model management schema mappings