A note on the reduction of two-way automata to one-way atuomata
Information Processing Letters
POPL '88 Proceedings of the 15th ACM SIGPLAN-SIGACT symposium on Principles of programming languages
Answering queries using views (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
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
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
Database techniques for the World-Wide Web: a survey
ACM SIGMOD Record
Data on the Web: from relations to semistructured data and XML
Data on the Web: from relations to semistructured data and XML
On the content of materialized aggregate views
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
Answering queries using views with arithmetic comparisons
Proceedings of the twenty-first ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Proceedings of the twenty-first ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Introduction To Automata Theory, Languages, And Computation
Introduction To Automata Theory, Languages, And Computation
IEEE Transactions on Knowledge and Data Engineering
Information Integration Using Logical Views
ICDT '97 Proceedings of the 6th International Conference on Database Theory
ICDT '97 Proceedings of the 6th International Conference on Database Theory
A Formal Perspective on the View Selection Problem
Proceedings of the 27th International Conference on Very Large Data Bases
Answering queries using views: A survey
The VLDB Journal — The International Journal on Very Large Data Bases
Proceedings of the twenty-second ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
View-Based Query Processing and Constraint Satisfaction
LICS '00 Proceedings of the 15th Annual IEEE Symposium on Logic in Computer Science
Answering Regular Path Queries Using Views
ICDE '00 Proceedings of the 16th International Conference on Data Engineering
Reasoning on regular path queries
ACM SIGMOD Record
Towards practically feasible answering of regular path queries in lav data integration
Proceedings of the sixteenth ACM conference on Conference on information and knowledge management
Joining the results of heterogeneous search engines
Information Systems
Relative information completeness
Proceedings of the twenty-eighth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Computing certain answers in the presence of dependencies
Information Systems
Relative information completeness
ACM Transactions on Database Systems (TODS)
Certain answers and rewritings for local regular path queries on graph-structured data
Proceedings of the Fourteenth International Database Engineering & Applications Symposium
Efficient processing of monotonic linear progressive queries via dynamic materialized views
Proceedings of the 2010 Conference of the Center for Advanced Studies on Collaborative Research
Certain answers for views and queries expressed as non-recursive datalog programs with negation
ACIIDS'11 Proceedings of the Third international conference on Intelligent information and database systems - Volume Part I
View determinacy for preserving selected information in data transformations
Information Systems
View-based query answering in Description Logics: Semantics and complexity
Journal of Computer and System Sciences
A materialized-view based technique to optimize progressive queries via dependency analysis
Proceedings of the 2011 Conference of the Center for Advanced Studies on Collaborative Research
CASCON '12 Proceedings of the 2012 Conference of the Center for Advanced Studies on Collaborative Research
Query processing under GLAV mappings for relational and graph databases
Proceedings of the VLDB Endowment
Hi-index | 5.24 |
As a result of the extensive research in view-based query processing, three notions have been identified as fundamental, namely rewriting, answering, and losslessness. Answering amounts to computing the tuples satisfying the query in all databases consistent with the views. Rewriting consists in first reformulating the query in terms of the views and then evaluating the rewriting over the view extensions. Losslessness holds if we can answer the query by solely relying on the content of the views. While the mutual relationship between these three notions is easy to identify in the case of conjunctive queries, the terrain of notions gets considerably more complicated going beyond such a query class. In this paper, we revisit the notions of answering, rewriting, and losslessness and clarify their relationship in the setting of semistructured databases, and in particular for the basic query class in this setting, i.e., two-way regular path queries. Our first result is a clean explanation of the relationship between answering and rewriting, in which we characterize rewriting as a ''linear approximation'' of query answering. We show that applying this linear approximation to the constraint-satisfaction framework yields an elegant automata-theoretic approach to query rewriting. As for losslessness, we show that there are indeed two distinct interpretations for this notion, namely with respect to answering, and with respect to rewriting. We also show that the constraint-theoretic approach and the automata-theoretic approach can be combined to give algorithmic characterization of the various facets of losslessness. Finally, we deal with the problem of coping with loss, by considering mechanisms aimed at explaining lossiness to the user.