On conjunctive queries containing inequalities
Journal of the ACM (JACM)
Using powerdomains to generalize relational databases
Theoretical Computer Science
On the equivalence of recursive and nonrecursive datalog programs
PODS '92 Proceedings of the eleventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
The complexity of querying indefinite data about linearly ordered domains
PODS '92 Proceedings of the eleventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Semantic representations and query languages for or-sets
PODS '93 Proceedings of the twelfth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Optimization of real conjunctive queries
PODS '93 Proceedings of the twelfth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Equivalence of datalog queries is undecidable
Journal of Logic Programming
Constraint checking with partial information
PODS '94 Proceedings of the thirteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Containment of conjunctive queries: beyond relations as sets
ACM Transactions on Database Systems (TODS)
A query language and optimization techniques for unstructured data
SIGMOD '96 Proceedings of the 1996 ACM SIGMOD international conference on Management of data
Deciding containment for queries with complex objects (extended abstract)
PODS '97 Proceedings of the sixteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Query containment for conjunctive queries with regular expressions
PODS '98 Proceedings of the seventeenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Navigational plans for data integration
AAAI '99/IAAI '99 Proceedings of the sixteenth national conference on Artificial intelligence and the eleventh Innovative applications of artificial intelligence conference innovative applications of artificial intelligence
Equivalences Among Relational Expressions with the Union and Difference Operators
Journal of the ACM (JACM)
SilkRoute: trading between relations and XML
Proceedings of the 9th international World Wide Web conference on Computer networks : the international journal of computer and telecommunications netowrking
Minimization of tree pattern queries
SIGMOD '01 Proceedings of the 2001 ACM SIGMOD international conference on Management of data
Containment and equivalence for an XPath fragment
Proceedings of the twenty-first ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Data integration: a theoretical perspective
Proceedings of the twenty-first ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Information Integration Using Logical Views
ICDT '97 Proceedings of the 6th International Conference on Database Theory
Adding Structure to Unstructured Data
ICDT '97 Proceedings of the 6th International Conference on Database Theory
Queries Independent of Updates
VLDB '93 Proceedings of the 19th International Conference on Very Large Data Bases
Verifying Integrity Constraints on Web Sites
IJCAI '99 Proceedings of the Sixteenth International Joint Conference on Artificial Intelligence
Answering queries using views: A survey
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
Mapping data in peer-to-peer systems: semantics and algorithmic issues
Proceedings of the 2003 ACM SIGMOD international conference on Management of data
Efficient query reformulation in peer data management systems
SIGMOD '04 Proceedings of the 2004 ACM SIGMOD international conference on Management of data
Verification of knowledge bases based on containment checking
AAAI'96 Proceedings of the thirteenth national conference on Artificial intelligence - Volume 1
XQuery containment in presence of variable binding dependencies
WWW '05 Proceedings of the 14th international conference on World Wide Web
Deciding well-definedness of XQuery fragments
Proceedings of the twenty-fourth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Heuristic containment check of partial tree-pattern queries in the presence of index graphs
CIKM '06 Proceedings of the 15th ACM international conference on Information and knowledge management
Optimization of nested XQuery expressions with orderby clauses
Data & Knowledge Engineering
On deciding well-definedness for query languages on trees
Journal of the ACM (JACM)
MQX: multi-query engine for compressed XML data
SIGIR '07 Proceedings of the 30th annual international ACM SIGIR conference on Research and development in information retrieval
Structured materialized views for XML queries
VLDB '07 Proceedings of the 33rd international conference on Very large data bases
Proceedings of the 17th ACM conference on Information and knowledge management
A heuristic approach for checking containment of generalized tree-pattern queries
Proceedings of the 17th ACM conference on Information and knowledge management
Containment of partially specified tree-pattern queries in the presence of dimension graphs
The VLDB Journal — The International Journal on Very Large Data Bases
Equivalence of nested queries with mixed semantics
Proceedings of the twenty-eighth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Containment and minimization of RDF/S query patterns
ISWC'05 Proceedings of the 4th international conference on The Semantic Web
EDBT'06 Proceedings of the 2006 international conference on Current Trends in Database Technology
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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 (number of sibling sub-blocks) to be 1. We prove that for arbitrary fanout, containment is coNP-hard already for queries with nesting depth 2, even if the query does not include variables in the return clauses. We then show that for queries with fixed nesting depth, containment is coNP-complete. Next, we establish the computational complexity of query containment for several practical extensions of c-XQueries, including queries with union and arithmetic comparisons, and queries where the XPath expressions may include descendant edges and negation. Finally, we describe a few heuristics for speeding up query containment checking in practice by exploiting properties of the queries and the underlying schema.