XPath Rewriting Using Multiple Views

Abstract

We study the problem of tree pattern query rewriting using multiple views for the class of tree patterns in P{//,[]}. Previous work has considered the rewriting problem using a single view. We consider two different ways of combining multiple views, define rewritings of a tree pattern using these combinations, and study the relationship between them. We show that when rewritings using single views do not exist, we may use such combinations of multiple views to rewrite a query, and even if rewritings using single views do exist, the rewritings using combinations of multiple views may provide more answers than those provided by the union of the rewritings using the individual views. We also study properties of intersections of tree patterns, and present algorithms for finding rewritings using intersections of views.