8,368 research outputs found
Simplification of many-valued logic formulas using anti-links
We present the theoretical foundations of the many-valued
generalization of a technique for simplifying large non-clausal
formulas in propositional logic, that is called "removal of
anti-links". Possible applications of anti-links include computation
of prime implicates of large non-clausal formulas as required, for
example, in diagnosis. Anti-links do not compute any normal form of a
given formula themselves, rather, they remove certain forms of
redundancy from formulas in negation normal form (NNF). Their main
advantage is that no clausal normal form has to be computed in order
to remove redundant parts of a formula. In this paper, we define an
anti-link operation on a generic language for expressing many-valued
logic formulas called "signed NNF" and we show that all interesting
properties of two-valued anti-links generalize to the many-valued
setting, although in a non-trivial way
Negation and Dichotomy
The present contribution might be regarded as a kind of defense of the common sense in logic. It is demonstrated that if the classical negation is interpreted as the minimal negation with n = 2 truth values, then deviant logics can be conceived as extension of the classical bivalent frame. Such classical apprehension of negation is possible in non- classical logics as well, if truth value is internalized and bivalence is replaced by bipartition
A Polynomial Translation of Logic Programs with Nested Expressions into Disjunctive Logic Programs: Preliminary Report
Nested logic programs have recently been introduced in order to allow for
arbitrarily nested formulas in the heads and the bodies of logic program rules
under the answer sets semantics. Nested expressions can be formed using
conjunction, disjunction, as well as the negation as failure operator in an
unrestricted fashion. This provides a very flexible and compact framework for
knowledge representation and reasoning. Previous results show that nested logic
programs can be transformed into standard (unnested) disjunctive logic programs
in an elementary way, applying the negation as failure operator to body
literals only. This is of great practical relevance since it allows us to
evaluate nested logic programs by means of off-the-shelf disjunctive logic
programming systems, like DLV. However, it turns out that this straightforward
transformation results in an exponential blow-up in the worst-case, despite the
fact that complexity results indicate that there is a polynomial translation
among both formalisms. In this paper, we take up this challenge and provide a
polynomial translation of logic programs with nested expressions into
disjunctive logic programs. Moreover, we show that this translation is modular
and (strongly) faithful. We have implemented both the straightforward as well
as our advanced transformation; the resulting compiler serves as a front-end to
DLV and is publicly available on the Web.Comment: 10 pages; published in Proceedings of the 9th International Workshop
on Non-Monotonic Reasonin
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