Processing XML Queries with Tree Signatures

With the rapidly increasing popularity of XML for data representation, there is a lot of interest in query processing over data that conforms to a labeled-tree data model. A variety of languages have been proposed for this purpose, all of which can be viewed as consisting of a pattern language and construction expressions. Since the data objects are typically trees, tree pattern matching is the central issue. The idea behind evaluating tree pattern queries, sometimes called twig queries, is to find all the ways of embedding the pattern in the data. Because this lies at the core of most languages for processing XML data, efficient evaluation techniques for these languages require appropriate indexing structures.