On supporting containment queries in relational database management systems
SIGMOD '01 Proceedings of the 2001 ACM SIGMOD international conference on Management of data
XRel: a path-based approach to storage and retrieval of XML documents using relational databases
ACM Transactions on Internet Technology (TOIT)
Holistic twig joins: optimal XML pattern matching
Proceedings of the 2002 ACM SIGMOD international conference on Management of data
Relational Databases for Querying XML Documents: Limitations and Opportunities
VLDB '99 Proceedings of the 25th 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
Efficient processing of XML twig queries with OR-predicates
SIGMOD '04 Proceedings of the 2004 ACM SIGMOD international conference on Management of data
On boosting holism in XML twig pattern matching using structural indexing techniques
Proceedings of the 2005 ACM SIGMOD international conference on Management of data
From region encoding to extended dewey: on efficient processing of XML twig pattern matching
VLDB '05 Proceedings of the 31st international conference on Very large data bases
Semantic querying of tree-structured data sources using partially specified tree patterns
Proceedings of the 14th ACM international conference on Information and knowledge management
Twig2Stack: bottom-up processing of generalized-tree-pattern queries over XML documents
VLDB '06 Proceedings of the 32nd international conference on Very large data bases
Efficiently Querying Large XML Data Repositories: A Survey
IEEE Transactions on Knowledge and Data Engineering
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
Holistic twig joins on indexed XML documents
VLDB '03 Proceedings of the 29th international conference on Very large data bases - Volume 29
Indexing XML data stored in a relational database
VLDB '04 Proceedings of the Thirtieth international conference on Very large data bases - Volume 30
VERT: a semantic approach for content search and content extraction in XML query processing
ER'07 Proceedings of the 26th international conference on Conceptual modeling
The VLDB Journal — The International Journal on Very Large Data Bases
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Twig pattern is considered a core pattern for XML queries. However, due to the limited expressivity of twig pattern expressions, many queries that aim to find complex output information under one object cannot be expressed in a single twig pattern. Instead, they have to be expressed as XQuery expression, which is transformed into several twig patterns linked by joins. To process such an XQuery query, we need to match multiple twig patterns to the XML document, even though they are all centered on the same object. In this paper we analyze the characteristics of each query node, i.e. the purpose, optionality and occurrence, and define four types of nodes in a twig pattern query to express output information, namely, output node, optional-output node, predicatedoutput node, and optional-predicated-output node. Then we propose the TP+Output expression to extend twig pattern queries, to model complex output information based on the semantics of different node types. With TP+Output, queries with the four output types can be expressed in one TP+Output expression and processed more efficiently. We extend our previously proposed twig pattern query processing algorithm, VERT, to process the TP+Output query, and demonstrate the performance improvement of using TP+Output to represent queries.