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On the Expressive Power of the Relational Algebra on Finite Sets of Relation Pairs
June 2009 (vol. 21 no. 6)
pp. 939-942
George H.L. Fletcher, Washington State University, Vancouver
Marc Gyssens, Hasselt University and the Transnational University of Limburg, Diepenbeek
Jan Paredaens, University of Antwerp, Antwerp
Dirk Van Gucht, Indiana University, Bloomington
We give a language-independent characterization of the expressive power of the relational algebra on finite sets of source-target relation instance pairs. The associated decision problem is shown to be cograph-isomorphism hard and in coNP. The main result is also applied in providing a new characterization of the generic relational queries.

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Index Terms:
Query languages, relational algebra, data mapping, data integration, definability, expressibility, BP completeness, graph isomorphism, genericity, monotonicity.
Citation:
George H.L. Fletcher, Marc Gyssens, Jan Paredaens, Dirk Van Gucht, "On the Expressive Power of the Relational Algebra on Finite Sets of Relation Pairs," IEEE Transactions on Knowledge and Data Engineering, vol. 21, no. 6, pp. 939-942, June 2009, doi:10.1109/TKDE.2008.221
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