Scalable data exchange with functional dependencies

  • Authors:

  • Bruno Marnette;Giansalvatore Mecca;Paolo Papotti

  • Affiliations:

  • Oxford University Computing Laboratory, UK and INRIA Saclay, France;Università della Basilicata -- Potenza, Italy;Università Roma Tre -- Roma, Italy

  • Venue:
  • Proceedings of the VLDB Endowment
  • Year:
  • 2010

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Abstract

The recent literature has provided a solid theoretical foundation for the use of schema mappings in data-exchange applications. Following this formalization, new algorithms have been developed to generate optimal solutions for mapping scenarios in a highly scalable way, by relying on SQL. However, these algorithms suffer from a serious drawback: they are not able to handle key constraints and functional dependencies on the target, i.e., equality generating dependencies (egds). While egds play a crucial role in the generation of optimal solutions, handling them with first-order languages is a difficult problem. In fact, we start from a negative result: it is not always possible to compute solutions for scenarios with egds using an SQL script. Then, we identify many practical cases in which this is possible, and develop a best-effort algorithm to do this. Experimental results show that our algorithm produces solutions of better quality with respect to those produced by previous algorithms, and scales nicely to large databases.