Query rewriting for semistructured data
SIGMOD '99 Proceedings of the 1999 ACM SIGMOD international conference on Management of data
Integrating keyword search into XML query processing
Proceedings of the 9th international World Wide Web conference on Computer networks : the international journal of computer and telecommunications netowrking
Flexible queries over semistructured data
PODS '01 Proceedings of the twentieth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Minimization of tree pattern queries
SIGMOD '01 Proceedings of the 2001 ACM SIGMOD international conference on Management of data
Containment and equivalence for an XPath fragment
Proceedings of the twenty-first ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Proceedings of the 2002 ACM SIGMOD international conference on Management of data
Efficient algorithms for minimizing tree pattern queries
Proceedings of the 2002 ACM SIGMOD international conference on Management of data
EDBT '02 Proceedings of the 8th International Conference on Extending Database Technology: Advances in Database Technology
Containment for XPath Fragments under DTD Constraints
ICDT '03 Proceedings of the 9th International Conference on Database Theory
Querying XML Documents Made Easy: Nearest Concept Queries
Proceedings of the 17th International Conference on Data Engineering
Views in a Large Scale XML Repository
Proceedings of the 27th International Conference on Very Large Data Bases
EDBT '02 Proceedings of the Worshops XMLDM, MDDE, and YRWS on XML-Based Data Management and Multimedia Engineering-Revised Papers
XPath Containment in the Presence of Disjunction, DTDs, and Variables
ICDT '03 Proceedings of the 9th International Conference on Database Theory
FleXPath: flexible structure and full-text querying for XML
SIGMOD '04 Proceedings of the 2004 ACM SIGMOD international conference on Management of data
SIGMOD '04 Proceedings of the 2004 ACM SIGMOD international conference on Management of data
XQuery containment in presence of variable binding dependencies
WWW '05 Proceedings of the 14th international conference on World Wide Web
Semantic querying of tree-structured data sources using partially specified tree patterns
Proceedings of the 14th ACM international conference on Information and knowledge management
Containment of Partially Specified Tree-Pattern Queries
SSDBM '06 Proceedings of the 18th International Conference on Scientific and Statistical Database Management
Answering tree pattern queries using views
VLDB '06 Proceedings of the 32nd international conference on Very large data bases
Heuristic containment check of partial tree-pattern queries in the presence of index graphs
CIKM '06 Proceedings of the 15th ACM international conference on Information and knowledge management
Forward node-selecting queries over trees
ACM Transactions on Database Systems (TODS)
Identifying meaningful return information for XML keyword search
Proceedings of the 2007 ACM SIGMOD international conference on Management of data
XSEarch: a semantic search engine for XML
VLDB '03 Proceedings of the 29th international conference on Very large data bases - Volume 29
VLDB '04 Proceedings of the Thirtieth international conference on Very large data bases - Volume 30
On testing satisfiability of tree pattern queries
VLDB '04 Proceedings of the Thirtieth international conference on Very large data bases - Volume 30
Containment of nested XML queries
VLDB '04 Proceedings of the Thirtieth international conference on Very large data bases - Volume 30
Assigning semantics to partial tree-pattern queries
Data & Knowledge Engineering
XML subtree queries: specification and composition
DBPL'05 Proceedings of the 10th international conference on Database Programming Languages
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Query processing techniques for XML data have focused mainly on tree-pattern queries (TPQs). However, the need for querying XML data sources whose structure is very complex or not fully known to the user, and the need to integrate multiple XML data sources with different structures have driven, recently, the suggestion of query languages that relax the complete specification of a tree pattern. In order to implement the processing of such languages in current DBMSs, their containment problem has to be efficiently solved. In this paper, we consider a query language which generalizes TPQs by allowing the partial specification of a tree pattern. Partial tree-pattern queries (PTPQs) constitute a large fragment of XPath that flexibly permits the specification of a broad range of queries from keyword queries without structure, to queries with partial specification of the structure, to complete TPQs. We address the containment problem for PTPQs. This problem becomes more complex in the context of PTPQs because the partial specification of the structure allows new, non-trivial, structural expressions to be inferred from those explicitly specified in a query. We show that the containent problem cannot be characterized by homomorphisms between PTPQs, even when PTPQs are put in a canonical form that comprises all derived structural expressions. We provide necessary and sufficient conditions for this problem in terms of homomorphisms between PTPQs and (a possibly exponential number of) TPQs. To cope with the high complexity of PTPQ containment, we suggest a heuristic approach for this problem that trades accuracy for speed. An extensive experimental evaluation of our heuristic shows that our heuristic approach can be efficiently implemented in a query optimizer.