Chapter 12: Performance Evaluation of Logic Programs 469
rules are then used to produce the optimized set of rules. Both these steps are
now directed, however, by the notion of sideways information passing graphs
(sips).
A sip corresponding to the above rule which binds Ζ is:
A -*»
x
ö.l, Α,α.1
z
a.2
The predicate A denotes the bound part of the head. This graph indicates that
the head binds X and this is used in solving the first occurrence of a. Further,
this solution is used to bind Ζ in solving the second occurrence of a. This
generates the adorned rule:
α*(Χ,Υ) :-α*(Χ,Ζ), a
bf
(Z,Y).
The magic rules corresponding to the two occurrences o ...
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