Elsevier

Theoretical Computer Science

Volume 76, Issue 1, 31 October 1990, Pages 143-177
Theoretical Computer Science

On the decomposition of datalog program mappings

https://doi.org/10.1016/0304-3975(90)90015-AGet rights and content
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Abstract

In an earlier paper one of the authors initiated an investigation into the composition of datalog program mappings in order to analyze serially executed datalog queries. In this paper, the reverse process of composition, namely decomposition, and related topics are examined. A number of results are presented and shown to be useful for the optimization of datalog queries. In particular, a canonical decomposition into (usually) smaller programs is given, as well as the decomposition of strongly linear programs and bounded programs into single-rule programs. The class of prime or nondecomposable programs is then introduced and scrutinized. Major results include the primality of a class of single-rule programs called symmetric, and the existence of arbitrarily large primes. Finally established are the decomposition of bounded programs into single-rule primes, and a condition for the uniqueness of decomposition into primes.

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Supported by the National Science Foundation under grants DCR-831-8752 and CCR-86-18907.

∗∗

This author's contribution was part of his Ph.D. Thesis. Present address: Computer Science Discipline, Flinders University of South Australia, Bedford Park, S.A. 5042, Australia.