On conjunctive queries containing inequalities
Journal of the ACM (JACM)
A note on the reduction of two-way automata to one-way atuomata
Information Processing Letters
Deciding equivalence of finite tree automata
SIAM Journal on Computing
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
Containment and minimization of positive conjunctive queries in OODB's
PODS '92 Proceedings of the eleventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
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
Sleepers and workaholics: caching strategies in mobile environments
SIGMOD '94 Proceedings of the 1994 ACM SIGMOD international conference on Management of data
Answering queries using views (extended abstract)
PODS '95 Proceedings of the fourteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Answering queries using templates with binding patterns (extended abstract)
PODS '95 Proceedings of the fourteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
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
Rewriting queries using views in description logics
PODS '97 Proceedings of the sixteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Answering recursive queries using views
PODS '97 Proceedings of the sixteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database 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
On the decidability of query containment under constraints
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
Catching the boat with Strudel: experiences with a Web-site management system
SIGMOD '98 Proceedings of the 1998 ACM SIGMOD international conference on Management of data
Combining Horn rules and description logics in CARIN
Artificial Intelligence
Rewriting aggregate queries using views
PODS '99 Proceedings of the eighteenth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
PODS '99 Proceedings of the eighteenth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Rewriting of regular expressions and regular path queries
PODS '99 Proceedings of the eighteenth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
WWW '99 Proceedings of the eighth international conference on World Wide Web
Equivalences Among Relational Expressions with the Union and Difference Operators
Journal of the ACM (JACM)
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
DTD inference for views of XML data
PODS '00 Proceedings of the nineteenth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
View-based query processing for regular path queries with inverse
PODS '00 Proceedings of the nineteenth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
A Web Odyssey: from Codd to XML
PODS '01 Proceedings of the twentieth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
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
Information Integration Using Logical Views
ICDT '97 Proceedings of the 6th International Conference on Database Theory
Conjunctive Query Containment Revisited
ICDT '97 Proceedings of the 6th International Conference on Database Theory
Tableau Techniques for Querying Information Sources through Global Schemas
ICDT '99 Proceedings of the 7th International Conference on Database Theory
Answering Queries Using Materialized Views with Disjunctions
ICDT '99 Proceedings of the 7th International Conference on Database Theory
Index Structures for Path Expressions
ICDT '99 Proceedings of the 7th International Conference on Database Theory
Answering Queries with Aggregation Using Views
VLDB '96 Proceedings of the 22th International Conference on Very Large Data Bases
Extended Temporal Logic Revisited
CONCUR '01 Proceedings of the 12th International Conference on Concurrency Theory
Answering Queries Using Views over Description Logics Knowledge Bases
Proceedings of the Seventeenth National Conference on Artificial Intelligence and Twelfth Conference on Innovative Applications of Artificial Intelligence
Optimization Properties for Classes of Conjunctive Regular Path Queries
DBPL '01 Revised Papers from the 8th International Workshop on Database Programming Languages
The GMAP: a versatile tool for physical data independence
The VLDB Journal — The International Journal on Very Large Data Bases
View-Based Query Processing and Constraint Satisfaction
LICS '00 Proceedings of the 15th Annual IEEE Symposium on Logic in Computer Science
Optimal implementation of conjunctive queries in relational data bases
STOC '77 Proceedings of the ninth annual ACM symposium on Theory of computing
Answering Regular Path Queries Using Views
ICDE '00 Proceedings of the 16th International Conference on Data Engineering
Algorithms for acyclic database schemes
VLDB '81 Proceedings of the seventh international conference on Very Large Data Bases - Volume 7
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
Proceedings of the twenty-second ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
PCK50 Proceedings of the Paris C. Kanellakis memorial workshop on Principles of computing & knowledge: Paris C. Kanellakis memorial workshop on the occasion of his 50th birthday
Reasoning on regular path queries
ACM SIGMOD Record
Containment and equivalence for a fragment of XPath
Journal of the ACM (JACM)
Decidable containment of recursive queries
Theoretical Computer Science - Database theory
Deciding equivalences among conjunctive aggregate queries
Journal of the ACM (JACM)
XPath satisfiability in the presence of DTDs
Journal of the ACM (JACM)
Conjunctive query containment and answering under description logic constraints
ACM Transactions on Computational Logic (TOCL)
HCH for checking containment of XPath fragment
Journal of Computer Science and Technology
A Program Slicing Based Method to Filter XML/DTD Documents
SOFSEM '07 Proceedings of the 33rd conference on Current Trends in Theory and Practice of Computer Science
Computer Languages, Systems and Structures
An Automata-Theoretic Approach to Regular XPath
DBPL '09 Proceedings of the 12th International Symposium on Database Programming Languages
EDBT'06 Proceedings of the 2006 international conference on Current Trends in Database Technology
Information retrieval from distributed semistructured documents using metadata interface
KDXD'06 Proceedings of the First international conference on Knowledge Discovery from XML Documents
Schema mappings and data exchange for graph databases
Proceedings of the 16th International Conference on Database Theory
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The basic querying mechanism over semistructured data, namely regular path queries, asks for all pairs of objects that are connected by a path conforming to a regular expression. We consider conjunctive two-way regular path queries (C2RPQc's), which extend regular path queries with two features. First, they add the inverse operator, which allows for expressing navigations in the database that traverse the edges both backward and forward. Second, they allow for using conjunctions of atoms, where each atom specifies that a regular path query with inverse holds between two terms, where each term is either a variable or a constant. For such queries we address the problem of view-based query answering, which amounts to computing the result of a query only on the basis of a set of views. More specifically, we present the following results: (1) We exhibit a mutual reduction between query containment and the recognition problem for view-based query answering for C2RPQc's, i.e., checking whether a given tuple is in the certain answer to a query. Based on such a result, we can show that the problem of view-based query answering for C2RPQc's is EXPSPACE-complete. (2) By exploiting techniques based on alternating two-way automata we show that for the restricted class of tree two-way regular path queries (in which the links between variables form a tree), query containment and view-based query answering are, rather surprisingly, in PSPACE (and hence, PSPACE-complete). (3) We present a technique to obtain view-based query answering algorithms that compute the whole set of tuples in the certain answer, instead of requiring to check each tuple separately. The technique is parametric wrt the query language, and can be applied both to C2RPQc's and to tree-queries.