Optimization of nested SQL queries revisited
SIGMOD '87 Proceedings of the 1987 ACM SIGMOD international conference on Management of data
On optimizing an SQL-like nested query
ACM Transactions on Database Systems (TODS)
XQuery formal semantics state and challenges
ACM SIGMOD Record
A Semi-monad for Semi-structured Data
ICDT '01 Proceedings of the 8th International Conference on Database Theory
VLDB '87 Proceedings of the 13th International Conference on Very Large Data Bases
Answering XML Queries on Heterogeneous Data Sources
Proceedings of the 27th International Conference on Very Large Data Bases
Reformulating XPath queries and XSLT queries on XSLT views
Data & Knowledge Engineering
Towards a physical XML independent XQuery/SQL/XML engine
Proceedings of the VLDB Endowment
Shifting Predicates to Inner Sub-expressions for XQuery Optimization
Advanced Internet Based Systems and Applications
SOFSEM'06 Proceedings of the 32nd conference on Current Trends in Theory and Practice of Computer Science
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Today it is widely recognized that optimization based on rewriting leads to faster query execution. The role of a query rewriting grows significantly when a query defined in terms of some view is processed. Using views is a good idea for building flexible virtual data integration systems with declarative query support. At present time such systems tend to be based on the XML data model and use XML as the internal data representation for processing query over heterogeneous data. Hence an elaborated algorithm of query rewriting is of great importance for efficient processing of XML declarative queries. This paper describes the query rewriting techniques for the XQuery language that is implemented as part of the BizQuery virtual data integration system. The goals of XQuery rewriting are stated. Query rewriting rules for FLWR expressions and for recursive XQuery functions are presented. Also the role of the XML schema in query rewriting is discussed.