The Semijoin Algebra and the Guarded Fragment
Journal of Logic, Language and Information, pp. 331-343, 2005.
databasesrelational algebrasemijoinguarded logic
In the 1970s Codd introduced the relational algebra, with operators selection, projection, union, difference and product, and showed that it is equivalent to first-order logic. In this paper, we show that if we replace in Codd's relational algebra the product operator by the "semijoin" operator, then the resulting "semijoin algebra" is eq...More
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