Semantic characterizations of navigational XPath

We give semantic characterizations of the expressive power of navigational XPath (a.k.a. Core XPath) in terms of first order logic. XPath can be used to specify sets of nodes and sets of paths in an XML document tree. We consider both uses. For sets of nodes, XPath is equally expressive as first order logic in two variables. For paths, 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.

[1]  Steven J. DeRose,et al.  XML Path Language (XPath) Version 1.0 , 1999 .

[2]  Dan Suciu,et al.  Containment and equivalence for an XPath fragment , 2002, PODS.

[3]  Makoto Murata,et al.  Extended path expressions of XML , 2001, PODS.

[4]  Thomas Schwentick,et al.  Expressive and efficient pattern languages for tree-structured data (extended abstract) , 2000, PODS '00.

[5]  Gabriel M. Kuper,et al.  Structural properties of XPath fragments , 2003, Theor. Comput. Sci..

[6]  Georg Gottlob,et al.  The complexity of XPath query evaluation , 2003, PODS.

[7]  Moshe Y. Vardi.  Why is Modal Logic So Robustly Decidable? , 1996, Descriptive Complexity and Finite Models.

[8]  M. de Rijke,et al.  A Proof System for Finite Trees , 1995, CSL.

[9]  P. Wadler.  Two semantics for XPath , 2000 .

[10]  Dan Suciu,et al.  Typechecking for XML transformers , 2000, J. Comput. Syst. Sci..

[11]  Richard Spencer-Smith,et al.  Modal Logic , 2007 .

[12]  Georg Gottlob,et al.  Monadic queries over tree-structured data , 2002, Proceedings 17th Annual IEEE Symposium on Logic in Computer Science.

[13]  Maarten Marx,et al.  First Order Paths in Ordered Trees , 2005, ICDT.

[14]  Maarten Marx,et al.  Conditional XPath, the first order complete XPath dialect , 2004, PODS.

[15]  Georg Gottlob,et al.  Conjunctive queries over trees , 2004, JACM.

[16]  M. de Rijke,et al.  CTL model checking for processing simple XPath queries , 2004, Proceedings. 11th International Symposium on Temporal Representation and Reasoning, 2004. TIME 2004..

[17]  Steven J. DeRose,et al.  XML Path Language (XPath) , 1999 .

[18]  Kousha Etessami,et al.  First-Order Logic with Two Variables and Unary Temporal Logic , 2002, Inf. Comput..

[19]  Frank Neven,et al.  A formal model for an expressive fragment of XSLT , 2000, Inf. Syst..