XML Query Languages

XPath. As the W3C standard for navigating XML documents, XPath has been widely used for specifying (e.g., XML Schema) and querying (e.g., XQuery, XSLT) XML data. In contrast to its regular-expression counterpart, a number of fundamental questions are open for XPath: for an XPath fragment commonly used in practice, is there a logic characterizing its expressive power? Is there a rewrite (or axiom) system for determining equivalence of XPath expressions? Is a fragment closed under Boolean operations ( closure properties under intersection, complementation)? Is there a normal form for a fragment? This project is to answer these questions. Results expected from the project are useful for, e.g., XML query optimization.

People:

Publications:

• XPath Satisfiability in the Presence of DTDs
  Journal of the ACM (JACM), to appear.
  Michael Benedikt, Wenfei Fan, Floris Geerts
  
  
• Query Translation from XPath to SQL in the Presence of Recursive DTDs.
  The 31st International Conference on Very Large Data Bases (VLDB), 2005
  Wenfei Fan, Jeffrey Xu Yu, Hongjun Lu, Jianhua Lu
  
  
• XPath satisfiability in the presence of DTDs
  ACM Symposium on Principles of Database Systems(PODS), 2005
  Michael Benedikt, Wenfei Fan, Floris Geerts
  
  
• Satisfiability of XPath Queries with Sibling Axes
  10th International Symposium on Database Programming Languages(DBPL), 2005
  Floris Geerts and Wenfei Fan
  
  
• Taming XPath Queries by Minimizing Wildcard Steps [.pdf]
  The 30th International Conference on Very Large Data Bases (VLDB), 2004
  Chee Yong Chan, Wenfei Fan, and Yiming Zeng
  
  
• Structural Properties of XPath Fragments [.pdf]
  The 9th International Conference on Database Theory (ICDT), 2003 LNCS 2572, pp. 79-95.
  Michael Benedikt, Wenfei Fan and Gabriel Kuper
  
  
• Tree Pattern Aggregation for Scalable XML Data Dissemination [.pdf]
  The 28th International Conference on Very Large Data Bases (VLDB), 2002
  Chee Yong Chan, Wenfei Fan, Pascal Felber, Minos Garofalakis, and Rajeev Rastogi
  
  
• Structural Properties of XPath Fragments [.pdf]
  Theoretical Computer Science (TCS), Volume 336, Issue 1, pp 3-31, May 2005.
  Michael Benedikt, Wenfei Fan, and Gabriel Kuper