On the expressive power of semijoin queries
Databases
2007-05-23 v2 Logic in Computer Science
Abstract
The semijoin algebra is the variant of the relational algebra obtained by replacing the join operator by the semijoin operator. We provide an Ehrenfeucht-Fraiss\'{e} game, characterizing the discerning power of the semijoin algebra. This game gives a method for showing that queries are not expressible in the semijoin algebra.
Keywords
Cite
@article{arxiv.cs/0308014,
title = {On the expressive power of semijoin queries},
author = {Dirk Leinders and Jerzy Tyszkiewicz and Jan Van den Bussche},
journal= {arXiv preprint arXiv:cs/0308014},
year = {2007}
}
Comments
9 pages, to appear in Information Processing Letters; added results that more clearly delineate the expressive power of SA, added a section that discusses the impact of order on the expressive power of SA, deemphasized the discussion on the relationship with GF