Abstract:
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In this paper we propose a new operational semantics, called BCN,
which is sound and complete with respect to Clark-Kunen's completion
for the unrestricted class of Normal Logic Programs. BCN is based on
constructive negation and can be seen as an operational semantics for
the class of Normal Constraint Logic Programs (NCLP) over the Herbrand
universe. The main features of BCN making it a useful operational
mechanism are twofold: First, BCN improves the existing proposals
because it is more amenable to a practical implementation. The point
is that, instead of computing subsidiary trees, the process of
constructing answers for negative goals is reduced to a simple
symbolic manipulation plus a constraint satisfaction checking process.
Essentially, our approach exploits the definition of negative literals
in the completion to interpret the constructive negation meta-rule.
Second, the way in which BCN is defined makes it an extensible scheme
to NCLP over arbitrary constraint domains. |