Efficient algorithms for minimizing tree pattern queries
Proceedings of the 2002 ACM SIGMOD international conference on Management of data
Containment for XPath Fragments under DTD Constraints
ICDT '03 Proceedings of the 9th International Conference on Database Theory
DataGuides: Enabling Query Formulation and Optimization in Semistructured Databases
VLDB '97 Proceedings of the 23rd International Conference on Very Large Data Bases
Tree pattern query minimization
The VLDB Journal — The International Journal on Very Large Data Bases
Optimal implementation of conjunctive queries in relational data bases
STOC '77 Proceedings of the ninth annual ACM symposium on Theory of computing
Structural Joins: A Primitive for Efficient XML Query Pattern Matching
ICDE '02 Proceedings of the 18th International Conference on Data Engineering
Implementing a scalable XML publish/subscribe system using relational database systems
SIGMOD '04 Proceedings of the 2004 ACM SIGMOD international conference on Management of data
Odysseus: A High-Performance ORDBMS Tightly-Coupled with IR Features
ICDE '05 Proceedings of the 21st International Conference on Data Engineering
Efficient algorithms for processing XPath queries
ACM Transactions on Database Systems (TODS)
Sequencing XML data and query twigs for fast pattern matching
ACM Transactions on Database Systems (TODS)
Evaluating structural summaries as access methods for XML
Proceedings of the 15th international conference on World Wide Web
Answering XML Queries Using Path-Based Indexes: A Survey
World Wide Web
A system for the static analysis of XPath
ACM Transactions on Information Systems (TOIS)
Covering indexes for XML queries: bisimulation - simulation = negation
VLDB '03 Proceedings of the 29th international conference on Very large data bases - Volume 29
From tree patterns to generalized tree patterns: on efficient evaluation of XQuery
VLDB '03 Proceedings of the 29th international conference on Very large data bases - Volume 29
Structured materialized views for XML queries
VLDB '07 Proceedings of the 33rd international conference on Very large data bases
On the minimization of XPath queries
Journal of the ACM (JACM)
A Novel Algorithm for Counting All Common Subsequences
GRC '07 Proceedings of the 2007 IEEE International Conference on Granular Computing
Path Summaries and Path Partitioning in Modern XML Databases
World Wide Web
Revisiting redundancy and minimization in an XPath fragment
EDBT '08 Proceedings of the 11th international conference on Extending database technology: Advances in database technology
Minimization of tree pattern queries with constraints
Proceedings of the 2008 ACM SIGMOD international conference on Management of data
A sampling approach for XML query selectivity estimation
Proceedings of the 12th International Conference on Extending Database Technology: Advances in Database Technology
Structural consistency: enabling XML keyword search to eliminate spurious results consistently
The VLDB Journal — The International Journal on Very Large Data Bases
A practitioner's approach to normalizing XQuery expressions
DASFAA'06 Proceedings of the 11th international conference on Database Systems for Advanced Applications
DASFAA'05 Proceedings of the 10th international conference on Database Systems for Advanced Applications
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Due to wide use of XPath, the problem of efficiently processing XPath queries has recently received a lot of attention. In particular, a considerable effort has been devoted to minimizing XPath queries since the efficiency of query processing greatly depends on the size of the query. Research work in this area can be classified into two categories: constraint-independent minimization and constraint-dependent minimization. The former minimizes queries in the absence of integrity constraints while the latter in the presence of them. For a linear path query, which is an XPath query without branching predicates, existing constraint-independent minimization methods are generally known to be unable to minimize the query without processing the query itself. Most recently, however, by using the DataGuide, a representative structural summary of XML data, a constraint-independent method that minimizes linear path queries in a top-down fashion has been proposed. Nevertheless, this method can fail to find a minimal query since it minimizes a query by merely erasing labels from the original query whereas a minimal query could include labels that are not present in the original query. In this paper, we propose a bottom-up approach called XMin that guarantees finding a minimal query for a given tree pattern query by using the DataGuide without processing the query itself. For the linear path query, we first show that the sequence of labels occurring in the minimal query is a subsequence of every schema label sequence that matches the original query. Here, the schema label sequence for a node is the sequence of labels from the root of XML data to the node. We then propose iterative subsequence generation that iteratively generates subsequences from the shortest schema label sequence matching the original query in a bottom-up fashion and tests query equivalence. Using iterative subsequence generation, we can always find a minimal query and we formally prove this guarantee. We also propose an extended algorithm that guarantees the minimality for the tree pattern query, which is a linear path query with branching predicates. These methods have been prototyped in a full-fledged object-relational DBMS. The experimental results using real and synthetic data sets show the practicality of our method.