
272
Chakravarthy, Grant,
and
Minker
some aspects of semantic query optimization for non-Horn and recursive
databases as well as for queries with universal quantification and negation.
Acknowledgments
We appreciate the excellent comments of the referees that led to considerable
improvement in the presentation of this paper. Work on this paper was sup-
ported by the National Science Foundation under grant numbers DCR 8305992
and DCR 8412662, and by the Army Research Office under grant number
DAAG-29-85-K-0177.
References
1.
Aho, Α. V., Sagiv, Y., and Ullman, J. D. [1979] Equivalences Among Relational
Expressions, Siam Journal of Computing 8 ,