Describing differences between databases

  • Authors:
  • Heiko Müller;Johann-Christoph Freytag;Ulf Leser

  • Affiliations:
  • Humboldt-Universität zu Berlin, Berlin, Germany;Humboldt-Universität zu Berlin, Berlin, Germany;Humboldt-Universität zu Berlin, Berlin, Germany

  • Venue:
  • CIKM '06 Proceedings of the 15th ACM international conference on Information and knowledge management
  • Year:
  • 2006

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Abstract

We study the novel problem of efficiently computing the update distance for a pair of relational databases. In analogy to the edit distance of strings, we define the update distance of two databases as the minimal number of set-oriented insert, delete and modification operations necessary to transform one database into the other. We show how this distance can be computed by traversing a search space of database instances connected by update operations. This insight leads to a family of algorithms that compute the update distance or approximations of it. In our experiments we observed that a simple heuristic performs surprisingly well in most considered cases.Our motivation for studying distance measures for databases stems from the field of scientific databases. There, replicas of a single database are often maintained at different sites, which typically leads to (accidental or planned) divergence of their content. To re-create a consistent view, these differences must be resolved. Such an effort requires an understanding of the process that produced them. We found that minimal update sequences of set-oriented update operations are a proper and concise representation of systematic errors, thus giving valuable clues to domain experts responsible for conflict resolution.