Exploiting conflict structures in inconsistent databases

  • Authors:

  • Solmaz Kolahi;Laks V. S. Lakshmanan

  • Affiliations:

  • University of British Columbia;University of British Columbia

  • Venue:
  • ADBIS'10 Proceedings of the 14th east European conference on Advances in databases and information systems
  • Year:
  • 2010

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Abstract

For an inconsistent database that violates a set of (conditional) functional dependencies, we define a basic conflict as a minimal set of attribute values, of which at least one needs to be changed in any attribute-based repair. Assuming that the collection of all basic conflicts is given, we show how we can exploit it in two important applications. The first application is cleaning the answer to a query by deciding whether a set of tuples is a possible answer, i.e., they are present in the result of the query applied to some minimal repair. We motivate an alternative notion of answer with a consistent derivation, which requires that the tuples are obtained through the same occurrences of attribute values in both the inconsistent database and the repair. The second application is cleaning data by generating repairs that are at a "reasonable" distance to the original database. Finally, we complement the above results and show that, if dependencies do not form a certain type of cycle, the cardinality of basic conflicts in any inconsistent database is bounded, and therefore it is possible to detect all basic conflicts in an inconsistent database in polynomial time in the size of input database.