Dan Olteanu
Abstract
Node-selecting queries over trees lie at the core of several important XML languages for the web, such as the node-selection language XPath, the query language XQuery, and the transformation language XSLT. The main syntactic constructs of such queries are the backward predicates, for example, ancestor and preceding, and the forward predicates, for example, descendant and following. Forward predicates are included in the depth-first, left-to-right preorder relation associated with the input tree, whereas backward predicates are included in the inverse of this preorder relation.
This work is devoted to an expressiveness study of node-selecting queries with proven theoretical and practical applicability, especially in the field of query evaluation against XML streams. The main question it answers positively is whether, for each input query with forward and backward predicates, there exists an equivalent forward-only output query. This question is then positively answered for input and output queries of varying structural complexity, using LOGLIN and PSPACE reductions.
Various existing applications based on the results of this work are reported, including query optimization and streamed evaluation.
- Abiteboul, S., Hull, R., and Vianu, V. 1995. Foundations of Databases. Addison-Wesley. Google Scholar
Digital Library
- Altinel, M. and Franklin, M. J. 2000. Efficient filtering of XML documents for selective dissemination of information. In Proceedings of the International Conference on Very Large Data Bases (VLDB). 53--64. Google ScholarDigital Library
- Amer-Yahia, S., Cho, S., Lakshmanan, L. V. S., and Srivastava, D. 2002. Tree pattern query minimization. VLDB J. 11, 4, 315--331. Google ScholarDigital Library
- Apache Project. 2001a. Cocoon 2.0: XML publishing framework. http://xml.apache.org/cocoon/index.html.Google Scholar
- Apache Project. 2001b. Xalan-Java, version 2.2. http://xml.apache.org/xalan-j/index.html.Google Scholar
- Baader, F. and Nipkow, T. 1998. Term Rewriting and All That. Cambridge University Press, New York. Google ScholarDigital Library
- Barton, C., Charles, P., Goyal, D., Raghavachari, M., Fontoura, M., and Josifovski, V. 2003. Streaming XPath processing with forward and backward axes. In Proceedings of the International Conference on Data Engineering (ICDE). 455--466.Google Scholar
- Benedikt, M., Fan, W., and Kuper, G. M. 2005. Structural properties of XPath fragments. Theor. Comput. Sci. 336, 1, 3--31. Google ScholarDigital Library
- Boag, S., Chamberlin, D., Fernandez, M. F., Florescu, D., Robie, J., and Siméon, J. 2006. XQuery 1.0: An XML query language. Candidate recommendation, World Wide Web Consortium.Google Scholar
- Bry, F., Coskun, F., Durmaz, S., Furche, T., Olteanu, D., and Spannagel, M. 2005. The XML stream query processor SPEX (demo). In Proceedings of the International Conference on Data Engineering (ICDE). http://spex.sourceforge.net. Google ScholarDigital Library
- Bry, F. and Kröger, P. 2003. A computational biology database digest: Data, data analysis, and data management. Distrib. Parallel Databases 13, 1, 7--42. Google ScholarDigital Library
- Chan, C.-Y., Felber, P., Garofalakis, M. N., and Rastogi, R. 2002. Efficient filtering of XML documents with XPath expressions. In Proceedings of the International Conference on Data Engineering (ICDE) 235--244. Google ScholarDigital Library
- Clark, J. 1999. XSL Transformations (XSLT) version 1.0. W3C recommendation, World Wide Web Consortium.Google Scholar
- Clark, J. and DeRose, S. 1999. XML path language (XPath) version 1.0. W3C recommendation, World Wide Web Consortium.Google Scholar
- DeRose, S., Jr., R. D., Grosso, P., Maler, E., Marsh, J., and Walsh, N. 2002. XML pointer language (XPointer). W3C recommendation, World Wide Web Consortium. http://www.w3.org/TR/xptr/.Google Scholar
- Desai, A. 2001. Introduction to sequential XPath. In Proceedings of the IDEAlliance XML Conference.Google Scholar
- Fallside, D. C. and Walmsley, P. 2001. XML-Schema. W3C recommendation, World Wide Web Consortium. http://www.w3.org/XML/Schema.Google Scholar
- Flesca, S., Furfaro, F., and Masciari, E. 2003. On the minimization of XPath queries. In Proceedings of the International Conference on Very Large Data Bases (VLDB). 153--164. Google ScholarDigital Library
- Gottlob, G., Koch, C., and Pichler, R. 2002. Efficient algorithms for processing XPath queries. In Proceedings of the International Conference on Very Large Data Bases (VLDB). 95--106. Google ScholarDigital Library
- Gottlob, G. and Koch, C. 2004. Monadic datalog and the expressive power of languages for web information extraction. J. ACM, 51, 1, 74--113. Google ScholarDigital Library
- Gottlob, G., Koch, C., and Schulz, K. 2006. Conjunctive queries over trees. J. ACM 53, 2. to appear. Google ScholarDigital Library
- Grust, T., van Keulen, M., and Teubner, J. 2004. Accelerating XPath evaluation in any RDBMS. ACM Trans. Database Syst. 29, 91--131. Google ScholarDigital Library
- Helmer, S., Kanne, C.-C., and Moerkotte, G. 2002. Optimized translation of XPath into algebraic expressions parameterized by programs containing navigational primitives. In Proceedings of the International Conference on Web Information Systems Engineering (WISE). 215--224. Google ScholarDigital Library
- Hidders, J. and Michiels, P. 2003. Avoiding unnecessary ordering operations in XPath. In Proceedings of the International Conference on Data Base Programming Languages (DBPL). 54--70.Google Scholar
- Ide, N., Bonhomme, P., and Romary, L. 2000. XCES: An XML-Based standard for linguistic corpora. In Proceedings of the Annual Conference on Language Resources and Evaluation (LREC) 825--830.Google Scholar
- Ives, Z. G., Halevy, A. Y., and Weld, D. S. 2002. An XML query engine for network-bound data. VLDB J. 11, 4, 380--402. Google ScholarDigital Library
- Kay, M. 2004. XSL Transformations (XSLT), version 2.0. Working draft, World Wide Web Consortium.Google Scholar
- Lincoln, P. and Christian, J. 1989. Adventures in associative-commutative unification. J. Symbol. Comput. 8, 1--2, 217--240. Google ScholarDigital Library
- Marian, A. and Siméon, J. 2003. Projecting XML documents. In Proceedings of the International Conference on Very Large Data Bases (VLDB). 213--224. Google ScholarDigital Library
- Marx, M. 2005. Conditional XPath. ACM Trans. Database Syst. to appear. Google ScholarDigital Library
- NASA. 2004. XML group resources page. http://xml.gsfc.nasa.gov/.Google Scholar
- Newman, M. H. A. 1942. On theories with a combinatorial definition of ‘equivalence’. Ann. Math. 43, 2, 223--243.Google ScholarCross Ref
- Olteanu, D. 2004. Evaluation of XPath queries against XML streams. Ph.D. thesis, University of Munich.Google Scholar
- Olteanu, D., Furche, T., and Bry, F. 2004. Evaluating complex queries against XML streams with polynomial combined complexity. In Proceedings of the Annual British National Conference on Databases (BNCOD). 31--44.Google Scholar
- Olteanu, D., Meuss, H., Furche, T., and Bry, F. 2002. XPath: Looking forward. In Proceedings of the EDBT Workshop XMLDM. 109--127. Lecture Notes in Computer Science vol. 2490. Springer Verlag. Google ScholarDigital Library
- Popa, L., Deutsch, A., and Tannen, V. 1999. Physical data independence, constraints, and optimization with universal plans. In Proceedings of the International Conference on Very Large Data Bases (VLDB). 459--470. Google ScholarDigital Library
- Raghavan, V., Deschler, K., and Rundensteiner, E. A. 2005. Vamana: A scalable cost-driven XPath engine. In International Workshop on XML Schema and Data Management (XSDM).Google Scholar
- Schott, S. and Noga, M. L. 2003. Lazy XSL transformations. In Proceedings of the ACM Symposium on Document Engineering. 9--18. Google ScholarDigital Library
- Wood, P. T. 2001. Minimizing simple XPath expressions. In Proceedings of the International Workshop on Web and Databases (WebDB). 13--18.Google Scholar
Index Terms
- Forward node-selecting queries over trees
Recommendations
Reformulating XPath queries and XSLT queries on XSLT views
Applications using XML for data representation very often use different XML formats and thus require the transformation of XML data. The common approach transforms entire XML documents from one format into another, e.g. by using an XSLT stylesheet. ...
Filtering unsatisfiable XPath queries
The satisfiability test checks, whether or not the evaluation of a query returns the empty set for any input document, and can be used in query optimization for avoiding the submission and the computation of unsatisfiable queries. Thus, applying the ...
Conjunctive queries over trees
We study the complexity and expressive power of conjunctive queries over unranked labeled trees represented using a variety of structure relations such as “child”, “descendant”, and “following” as well as unary relations for node labels. We establish a ...
Comments