Evaluating queries with generalized path expressions
SIGMOD '96 Proceedings of the 1996 ACM SIGMOD international conference on Management of data
On supporting containment queries in relational database management systems
SIGMOD '01 Proceedings of the 2001 ACM SIGMOD international conference on Management of data
APEX: an adaptive path index for XML data
Proceedings of the 2002 ACM SIGMOD international conference on Management of data
Storing and querying ordered XML using a relational database system
Proceedings of the 2002 ACM SIGMOD international conference on Management of data
Holistic twig joins: optimal XML pattern matching
Proceedings of the 2002 ACM SIGMOD international conference on Management of data
Optimizing Regular Path Expressions Using Graph Schemas
ICDE '98 Proceedings of the Fourteenth International Conference on Data Engineering
DataGuides: Enabling Query Formulation and Optimization in Semistructured Databases
VLDB '97 Proceedings of the 23rd International Conference on Very Large Data Bases
Indexing and Querying XML Data for Regular Path Expressions
Proceedings of the 27th International Conference on Very Large Data Bases
A Fast Index for Semistructured Data
Proceedings of the 27th International Conference on Very Large Data Bases
Structural Joins: A Primitive for Efficient XML Query Pattern Matching
ICDE '02 Proceedings of the 18th International Conference on Data Engineering
An evaluation of XML indexes for structural join
ACM SIGMOD Record
Efficient structural joins on indexed XML documents
VLDB '02 Proceedings of the 28th international conference on Very Large Data Bases
XMark: a benchmark for XML data management
VLDB '02 Proceedings of the 28th international conference on Very Large Data Bases
Holistic twig joins on indexed XML documents
VLDB '03 Proceedings of the 29th international conference on Very large data bases - Volume 29
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XML data usually consists of tree-structured hierarchical data, which affects the storing and searching mechanisms for XML. When storing XML data into databases the hierarchical relationships among XML nodes need to be considered. User’s search queries that specify hierarchical relationships among the nodes also require appropriate processing mechanisms. Structural join operations provide a solution to this problem by efficiently computing hierarchical relationships in XML databases based on the node numbering storage scheme. However, in order to process a branch query containing several hierarchical relationships on XML data, many structural joins need to be sequentially carried out and result in a high query execution cost. This paper proposes mechanisms to reduce the cost of processing branch pattern XML queries requiring multiple structural joins. We discuss two approaches for rewriting a query composed of a single branch, and then apply these approaches to general branch queries. The first approach uses the concept of equivalence class relationships among regular path expression queries. The second approach uses a bottom-up approach to reduce the overhead identified in the first scheme. Experimental results show that the proposed schemes can reduce the query execution cost by up to an order of magnitude of the original execution cost.