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The recovery of a schema mapping: bringing exchanged data back

Published:09 June 2008Publication History

ABSTRACT

A schema mapping is a specification that describes how data from a source schema is to be mapped to a target schema. Once the data has been transferred from the source to the target, a natural question is whether one can undo the process and recover the initial data, or at least part of it. In fact, it would be desirable to find a reverse schema mapping from target to source that specifies how to bring the exchanged data back.

In this paper, we introduce the notion of a recovery of a schema mapping: it is a reverse mapping M' for a mapping M that recovers sound data with respect to M. We further introduce an order relation on recoveries. This allows us to choose mappings that recover the maximum amount of sound information. We call such mappings maximum recoveries. We study maximum recoveries in detail, providing a necessary and sufficient condition for their existence. In particular, we prove that maximum recoveries exist for the class of mappings specified by FO-to-CQ source-to-target dependencies. This class subsumes the class of source-to-target tuple-generating dependencies used in previous work on data exchange. For the class of mappings specified by FO-to-CQ dependencies, we provide an exponential-time algorithm for computing maximum recoveries, and a simplified version for full dependencies that works in quadratic time. We also characterize the language needed to express maximum recoveries, and we include a detailed comparison with the notion of inverse (and quasi-inverse) mapping previously proposed in the data exchange literature. In particular, we show that maximum recoveries strictly generalize inverses. We study the complexity of some decision problems related to the notions of recovery and maximum recovery. Finally, we report our initial results about a relaxed

notion of maximal recovery, showing that it strictly generalizes the notion of maximum recovery.

References

  1. F. Afrati, C. Li, and V. Pavlaki. Data exchange with arithmetic comparisons. Technical report, UCI ICS, 2006.Google ScholarGoogle Scholar
  2. M. Arenas, P. Barceló, R. Fagin, and L. Libkin. Locally consistent transformations and query answering in data exchange. In PODS, pages 229--240, 2004. Google ScholarGoogle ScholarDigital LibraryDigital Library
  3. P. Bernstein. Applying model management to classical meta data problems. In CIDR, 2003.Google ScholarGoogle Scholar
  4. P. Bernstein and S. Melnik. Model management 2.0: manipulating richer mappings. In SIGMOD, pages 1--12, 2007. Google ScholarGoogle ScholarDigital LibraryDigital Library
  5. A. Deutsch and V. Tannen. Reformulation of XML queries and constraints. In ICDT, pages 225--241, 2003. Google ScholarGoogle ScholarDigital LibraryDigital Library
  6. R. Fagin. Horn clauses and database dependencies. JACM, 29(4):952--985, 1982. Google ScholarGoogle ScholarDigital LibraryDigital Library
  7. R. Fagin. Inverting schema mappings. TODS, 32(4), 2007. Google ScholarGoogle ScholarDigital LibraryDigital Library
  8. R. Fagin, P. G. Kolaitis, R. J. Miller, and L. Popa. Data exchange: semantics and query answering. TCS, 336(1):89--124, 2005. Google ScholarGoogle ScholarDigital LibraryDigital Library
  9. R. Fagin, P. G. Kolaitis, L. Popa, and W.-C. Tan. Composing schema mappings: second-order dependencies to the rescue. TODS, 30(4):994--1055, 2005. Google ScholarGoogle ScholarDigital LibraryDigital Library
  10. R. Fagin, P. G. Kolaitis, L. Popa, and W.-C. Tan. Quasi-inverses of schema mappings. In PODS, pages 123--132, 2007. Google ScholarGoogle ScholarDigital LibraryDigital Library
  11. G. De Giacomo, D. Lembo, M. Lenzerini, and R. Rosati. On reconciling data exchange, data integration, and peer data management. In PODS, pages 133--142, 2007. Google ScholarGoogle ScholarDigital LibraryDigital Library
  12. G. Gottlob and A. Nash. Data exchange: computing cores in polynomial time. In PODS, pages 40--49, 2006. Google ScholarGoogle ScholarDigital LibraryDigital Library
  13. P. G. Kolaitis, J. Panttaja, and W.-C. Tan. The complexity of data exchange. In PODS, pages 30--39, 2006. Google ScholarGoogle ScholarDigital LibraryDigital Library
  14. L. Libkin. Data exchange and incomplete information. In PODS, pages 60--69, 2006. Google ScholarGoogle ScholarDigital LibraryDigital Library
  15. S. Melnik. Generic Model Management: Concepts and Algorithms, volume 2967 of LNCS. Springer, 2004. Google ScholarGoogle ScholarDigital LibraryDigital Library
  16. S. Melnik, P. Bernstein, A. Y. Halevy, and E. Rahm. Supporting executable mappings in model management. In SIGMOD, pages 167--178, 2005. Google ScholarGoogle ScholarDigital LibraryDigital Library

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