Research on XML Query Optimization

XML has become the de-facto standard for data representation and exchange on the World-Wide Web. Due to the nature of information on the Web and the inherent flexibility of XML, it is expected that much of the data encoded in XML will be semi-structured. Data on the internet is increasingly presented in XML format which enables researches on various kinds of XML storage model. Meanwhile, XML query optimization has become a hot research topic in database field. This paper gives an overview of the current status of technology for XML query optimization. The features of XML query optimization and key problems of research are also discussed deeply. Main aspects of current work on XML query optimization include XML algebra, cost model, complex path selectivity estimation, statistics information, and so on. Finally, this paper prospects future research directions and presents some viewpoints of XML query optimization.