Acta Informatica

, Volume 24, Issue 2, pp 131–144 | Cite as

Losslessness and project-join constructibility in relational databases

  • G. Loizou
  • P. Thanisch
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Summary

Checking a database scheme for the lossless join property with respect to a set, M, of multivalued dependencies (MVDs) is NP-hard. We prove that, for a class of MVDs that includes the set of projected full MVDs, this check can be performed in polynomial time. Even with a lossless database scheme and a consistent database, joining the set of relations in the database can take time and space that is exponential in the size of the relation finally obtained. Joining the set of relations of such a database can be performed in polynomial time if the database scheme is project-join constructible with respect to M. We prove that project-join constructibility, a stricter condition than the lossless join property, can be detected in a database scheme in polynomial time.

Keywords

Information System Operating System Data Structure Communication Network Information Theory 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Springer-Verlag 1987

Authors and Affiliations

  • G. Loizou
    • 1
  • P. Thanisch
    • 2
  1. 1.Department of Computer ScienceBirkbeck College, University of LondonLondonUK
  2. 2.Department of Computer ScienceHeriot-Watt UniversityEdinburghScotland

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