Semantic characterizations of navigational XPath

We give semantic characterizations of the expressive power of navigational XPath (also called Core XPath) in terms of first order logic. XPath can be used to specify sets of nodes and to specify sets of paths in a document tree. We consider both uses. For sets of nodes, we show that first order logic in two variables is equally expressive as XPath. For paths, we show that XPath can be defined using four simple connectives, which together yield the class of first order definable relations which are safe for bisimulation. Furthermore, we give a characterization of the XPath expressible paths in terms of conjunctive queries.

• Type: Conference
• Year: 2005
• Where: SIGMOD
• Authors: Maarten Marx, Maarten de Rijke
• Keywords: Core XPath, Database, Navigational Xpath, SIGMOD 2005, XPath Expressible Paths