Rule ordering in bottom-up fixpoint evaluation of logic programs
Ramakrishnan, R.
Srivastava, D.
Sudarshan, S.
Dept. of Comput. Sci., Wisconsin Univ., Madison, WI;
This paper appears in: Knowledge and Data Engineering, IEEE Transactions on
Publication Date: Aug 1994
Volume: 6,
Issue: 4
On page(s): 501-517
ISSN: 1041-4347
References Cited: 26
INSPEC Accession Number: 4762961
Digital Object Identifier: 10.1109/69.298169
Current Version Published: 2002-08-06
Abstract
Logic programs can be evaluated bottom-up by repeatedly applying
all rules, in “iterations”, until the fixpoint is reached.
However, it is often desirable-and, in some cases, e.g. programs with
stratified negation, it is even necessary to guarantee the semantics-to
apply the rules in some order. We present two algorithms that apply
rules in a specified order without repeating inferences. One of them
(GSN) is capable of dealing with a wide range of rule orderings, but
with a little more overhead than the well-known seminaive algorithm
(which we call BSN). The other (PSN) handles a smaller class of rule
orderings, but with no overheads beyond those in BSN. We also
demonstrate that by choosing a good ordering, we can reduce the number
of rule applications (and thus the number of joins). We present a
theoretical analysis of rule orderings and identify orderings that
minimize the number of rule applications (for all possible instances of
the base relations) with respect to a class of orderings called fair
orderings. We also show that though nonfair orderings may do a little
better on some data sets, they can do much worse on others. The analysis
is supplemented by performance results
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