Query answering using views for XML

The problem of answering query using views is to find efficient methods of answering a query using a set of previously materialized views over the database, rather than accessing the database. As XML becomes the standard of data representation and exchange over the internet, the problem has recently drawn more attentions because of its relevance to a wide varieties of XML data management problems, there is a pressing needs to develop more techniques to solve it for XML data effectively and efficiently. We study a class of XPath queries and materialized views which may contain child, descendant axis and predicates. We first describe an algorithm to find the maximally-contained rewritings in the absence of database schema. We then present an efficient algorithm to search the maximally-contained rewriting under choice-free acyclic schema and prove the uniqueness of the maximally-contained rewriting. Finally we show its performance experimentally by extending our algorithm to answer queries in XQuery expression.Science, Faculty ofComputer Science, Department ofGraduat