Containment of Nested XML Queries

Query containment is the most fundamental relationship between a pair of database queries: a query Q is said to be contained in a query Q if the answer for Q is always a subset of the answer for Q , independent of the current state of the database. Query containment is an important problem in a wide variety of data management applications, including verification of integrity constraints, reasoning about contents of data sources in data integration, semantic caching, verification of knowledge bases, determining queries independent of updates, and most recently, in query reformulation for peer data management systems. Query containment has been studied extensively in the relational context and for XPath queries, but not for XML queries with nesting. We consider the theoretical aspects of the problem of query containment for XML queries with nesting. We begin by considering conjunctive XML queries (c-XQueries), and show that containment is in polynomial time if we restrict the fanout (...

• Type: Conference
• Year: 2004
• Where: VLDB
• Authors: Xin Dong, Alon Y. Halevy, Igor Tatarinov
• Keywords: Data Management, Database, Query Containment, VLDB 2004, XML Queries