Theoretical Computer Science
On conjunctive queries containing inequalities
Journal of the ACM (JACM)
Foundations of deductive databases and logic programming
Decidable optimization problems for database logic programs
STOC '88 Proceedings of the twentieth annual ACM symposium on Theory of computing
Equivalence of datalog queries is undecidable
Journal of Logic Programming
The complexity of querying indefinite information: defined relations, recursion and linear order
The complexity of querying indefinite information: defined relations, recursion and linear order
On the complexity of equivalence between recursive and nonrecursive Datalog programs
PODS '94 Proceedings of the thirteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Subsumption between queries to object-oriented databases
Information Systems - Special issue on extending database technology
Semantic query optimization in Datalog programs (extended abstract)
PODS '95 Proceedings of the fourteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Query caching and optimization in distributed mediator systems
SIGMOD '96 Proceedings of the 1996 ACM SIGMOD international conference on Management of data
A query language and optimization techniques for unstructured data
SIGMOD '96 Proceedings of the 1996 ACM SIGMOD international conference on Management of data
Panorama: a database system that annotates its answers to queries with their properties
Journal of Intelligent Information Systems
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
Complexity of answering queries using materialized views
PODS '98 Proceedings of the seventeenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Database techniques for the World-Wide Web: a survey
ACM SIGMOD Record
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
On the foundations of the universal relation model
ACM Transactions on Database Systems (TODS)
Computational problems related to the design of normal form relational schemas
ACM Transactions on Database Systems (TODS)
Equivalences Among Relational Expressions with the Union and Difference Operators
Journal of the ACM (JACM)
Data on the Web: from relations to semistructured data and XML
Data on the Web: from relations to semistructured data and XML
Regular path queries with constraints
Journal of Computer and System Sciences
Data integration: a theoretical perspective
Proceedings of the twenty-first ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Foundations of Databases: The Logical Level
Foundations of Databases: The Logical Level
Introduction To Automata Theory, Languages, And Computation
Introduction To Automata Theory, Languages, And Computation
Optimizing Queries with Materialized Views
ICDE '95 Proceedings of the Eleventh International Conference on Data Engineering
Verifying Integrity Constraints on Web Sites
IJCAI '99 Proceedings of the Sixteenth International Joint Conference on Artificial Intelligence
View-Based Query Answering and Query Containment over Semistructured Data
DBPL '01 Revised Papers from the 8th International Workshop on Database Programming Languages
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
The description logic handbook: theory, implementation, and applications
The description logic handbook: theory, implementation, and applications
Elementary induction on abstract structures (Studies in logic and the foundations of mathematics)
Elementary induction on abstract structures (Studies in logic and the foundations of mathematics)
Complexity and composition of synthesized web services
Proceedings of the twenty-seventh ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
The impact of virtual views on containment
Proceedings of the VLDB Endowment
Datalog for security, privacy and trust
Datalog'10 Proceedings of the First international conference on Datalog Reloaded
On the decidability and complexity of identity knowledge representation
DASFAA'12 Proceedings of the 17th international conference on Database Systems for Advanced Applications - Volume Part I
ICALP'12 Proceedings of the 39th international colloquium conference on Automata, Languages, and Programming - Volume Part II
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One of the most important reasoning tasks on queries is checking containment, i.e., verifying whether one query yields necessarily a subset of the result of another one. Query containment is crucial in several contexts, such as query optimization, query reformulation, knowledge-base verification, information integration, integrity checking, and cooperative answering. Containment is undecidable in general for Datalog, the fundamental language for expressing recursive queries. On the other hand, it is known that containment between monadic Datalog queries and between Datalog queries and unions of conjunctive queries are decidable. It is also known that containment between unions of conjunctive two-way regular path queries, which are queries used in the context of semistructured data models containing a limited form of recursion in the form of transitive closure, is decidable. In this paper, we combine the automata-theoretic techniques at the base of these two decidability results to show that containment of Datalog in union of conjunctive two-way regular path queries is decidable in 2EXPTIME. By sharpening a known lower bound result for containment of Datalog in union of conjunctive queries we show also a matching lower bound.