Querying techniques for XML data

XML has become the de facto standard for data representation and exchange for Web applications, such as digital library, Web service, and electronic business. How to retrieve interesting information from the promising XML data is an active research area. Among techniques in this area, the description of query patterns is a crucial section. This paper reviews the actualities of recent researches on this topic. It classifies the query descriptors into two categories, XML Query type and XML IR type (with three subcategories: XML IR/keyword, XML IR/fragment and XML IR/query), and concludes three popular problems: Twig pattern processing, SLCA (smallest lowest common ancestor) problem, and similarity measuring techniques for retrieved XML fragments. It analyzes the virtue and deficiency of related techniques based on their convenience for common users. And hereby it proposes four issues for further XML querying researches: structural keywords and corresponding structural similarity measuring, wiping off the redundancy in XML data processing between XML Query (including XML IR/query) and XML IR/keyword, theoretical discussion of XML Query and its realization, and the management of peculiar XML data.EI061400-14181