Andre Hernich
ABSTRACT
Data exchange deals with the following problem: given an instance over a source schema, a specification of the relationship between the source and the target,and dependencies on the target, construct an instance over a target schema that satisfies the given relationships and dependencies. Recently - for data exchange settings without target dependencies - Libkin (PODS'06) introduced a new concept of solutions based on the closed world assumption (so calledCWA-solutions), and showed that, in some respects, this new notion behaves better than the standard notion of solutions considered in previous papers on data exchange. The present paper extends Libkin's notion of CWA-solutions to data exchange settings with target dependencies. We show that, when restricting attention to data exchange settings with weakly acyclic target dependencies, this new notion behaves similarly as before: the core is the unique "minimal" CWA-solution, and computing CWA-solutions as well as certain answers to positive queries is possible in polynomial time and can be PTIME-hard. However, there may be more than one "maximal" CWA-solution. And going beyond the class of positive queries, we obtain that there are conjunctive queries with (just) one inequality, for which evaluating the certain answers is coNP-hard. Finally, we consider the EXISTENCE-OF-CWA-SOLUTIONS problem: while the problem is tractable for data exchange settings with weakly acyclic target dependencies, it turns out to be undecidable for general data exchange settings. As a consequence, we obtain that also the EXISTENCE-OF-UNIVERSAL-SOLUTIONS problem is undecidable in genera.
- M. Arenas, P. Barceló, R. Fagin, and L. Libkin. Locally consistent transformations and query answering in data exchange. In Proc. PODS'04, pages 229--240, 2004. Google Scholar
Digital Library
- M. Arenas and L. Libkin. XML data exchange: consistency and query answering. In Proc. PODS'05, pages 13--24, 2005. Google ScholarDigital Library
- A. K. Chandra and P. M. Merlin. Optimal implementation of conjunctive queries in relational data bases. In Proc. STOC'77, pages 77--90, 1977. Google ScholarDigital Library
- A. Deutsch and V. Tannen. Reformulation of XML queries and constraints. In Proc. ICDT'03, pages 225--241, 2003. Google ScholarDigital Library
- R. Fagin. Inverting schema mappings. In Proc. PODS'06, pages 50--59, 2006. Google ScholarDigital Library
- R. Fagin, P. G. Kolaitis, R. J. Miller, and L. Popa. Data exchange: semantics and query answering. Theoretical Computer Science, 336(1):89--124, 2005. Full version of ICDT'03 paper. Google ScholarCross Ref
- R. Fagin, P. G. Kolaitis, and L. Popa. Data exchange: getting to the core. ACM Transactions on Database Systems, 30(1):174--210, 2005. Full version of PODS'03 paper. Google ScholarDigital Library
- G. Gottlob and A. Nash. Data exchange: Computing cores in polynomial time. In Proc. PODS'06, pages 40--49, 2006. Google ScholarDigital Library
- P. Hell and J. Nešetńil. The core of a graph. Discrete Mathematics, 109:117--126, 1992. Google ScholarDigital Library
- P. G. Kolaitis. Schema mappings, data exchange, and metadata management. In Proc. PODS'05, pages 61--75, 2005. Google ScholarDigital Library
- P. G. Kolaitis, J. Panttaja, and W. C. Tan. The complexity of data exchange. In Proc. PODS'06, pages 30--39, 2006. Google ScholarDigital Library
- L. Libkin. Data exchange and incomplete information. In Proc. PODS'06, pages 60--69, 2006. Google ScholarDigital Library
- A. Madry. Data exchange: On the complexity of answering queries with inequalities. Information Processing Letters, 94:253--257, 2005. Google ScholarDigital Library
- R. van der Meyden. Logical approaches to incomplete information: A survey. In Logics for Databases and Information Systems, pages 307--356. Kluwer, 1998. Google ScholarDigital Library
Index Terms
- CWA-solutions for data exchange settings with target dependencies
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