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Abstract:
In set-based program analysis, one first infers a set constraint
$\phi$ from a program and then, in a constraint-solving process, one
transforms $\phi$ into an effective representation of sets of program
values. Heintze and Jaffar have thus analyzed logic programs with
respect to the least-model semantics. In this paper, we present a
set-based analysis of logic programs with respect to the greatest
model semantics, and we give its complexity characterization. We
consider set constraints consisting of inclusions $x\subseteq\tau$
between a variable $x$ and a term $\tau$ with intersection, union and
projection. We solve such a set constraint by computing a
representation of its greatest solution (essentially as a tree
automaton). We obtain that the problem of the emptiness of its
greatest solution is DEXPTIME-complete. The choice of the greatest
model for set-based analysis is motivated by the verification of
safety properties (``no failure'') of reactive (ie, possibly
non-terminating) logic programs over infinite trees. Therefore, we
account also for infinite trees.
