Magic Sets for the XPath Language

The eXtensible Markup Language (XML) is considered as the format of choice for the exchange of information among various applications on the Internet. Since XML is emerging as a standard for data exchange, it is natural that queries among applications should be expressed as queries against data in XML format. This use gives rise to a requirement for a query language expressly designed for XML resources. World Wide Web Consortium (W3C) convened to create the XQuery language, concretely, a typed functional language for querying XML documents. One key aspect of the XQuery language is the use of the XPath language as basis for handling the structure of an XML document. In this paper, we present a proposal for the representation of XML documents by means of a logic program. Rules and facts can be used for representing the document schema and the XML document itself. In addition, we study how to query by means of the XPath language against a logic program representing an XML document. It evolves the specialization of the logic program with regard to the XPath expression. This specialization technique is based on the well-known transformation technique called Magic Sets and studied for deductive databases. The bottom-up evaluation of the special