Efficient Evaluation of XML Path Queries with Automata

Path query is one of the most frequently used components by the various XML query languages. Most of the proposed methods compute path queries in instance space, i.e. directly facing the XML instances, such as XML tree traversal and containment join ways. As a query method based on automata technique, automata match (AM) can evaluate path expression queries in schema space so that it allows efficient computation of complex queries on vast amount of data. This paper introduces how to construct query automata in order to compute all regular expression queries including those with wildcards. Furthermore, a data structure named schema automata is proposed to evaluate containment queries that are very difficult from the conventional automata point of view. To improve the efficiency of schema automata, methods to reduce and persistent them are proposed. Finally, performance study of the proposed methods are given.