The Limits of Horn Logic Programs

Given a sequence $\{\Pi_n\}$ of Horn logic programs, the limit $\Pi$ of $\{\Pi_n\}$ is the set of the clauses such that every clause in $\Pi$ belongs to almost every $\Pi_n$ and every clause in infinitely many $\Pi_n$'s belongs to $\Pi$ also. The limit program $\Pi$ is still Horn but may be infinite. In this paper, we consider if the least Herbrand model of the limit of a given Horn logic program sequence $\{\Pi_n\}$ equals the limit of the least Herbrand models of each logic program $\Pi_n$. It is proved that this property is not true in general but holds if Horn logic programs satisfy an assumption which can be syntactically checked and be satisfied by a class of Horn logic programs. Thus, under this assumption we can approach the least Herbrand model of the limit $\Pi$ by the sequence of the least Herbrand models of each finite program $\Pi_n$. We also prove that if a finite Horn logic program satisfies this assumption, then the least Herbrand model of this program is recursive. Finally, by use of the concept of stability from dynamical systems, we prove that this assumption is exactly a sufficient condition to guarantee the stability of fixed points for Horn logic programs.Comment: 11 pages, added new results. Welcome any comments to [email protected]

Description of Fuzzy First-Order Modal Logic Based on Constant Domain Semantics

Abstract. As an extension of the traditional modal logic, the fuzzy first-order modal logic is discussed in this paper. A description of fuzzy first-order modal logic based on constant domain semantics is given, and a formal system of fuzzy reasoning based on the semantic information of models of first-order modal logic is established. It is also introduced in this paper the notion of the satisfiability of the reasoning system and some properties associated with the satisfiability are proved

The Correspondence between Propositional Modal Logic with Axiom □φ↔◊φ\Box\varphi \leftrightarrow \Diamond \varphi and the Propositional Logic

Part 5: Automatic ReasoningInternational audienceThe propositional modal logic is obtained by adding the necessity operator □ to the propositional logic. Each formula in the propositional logic is equivalent to a formula in the disjunctive normal form. In order to obtain the correspondence between the propositional modal logic and the propositional logic, we add the axiom $\Box\varphi \leftrightarrow\Diamond\varphi$ to K and get a new system K + . Each formula in such a logic is equivalent to a formula in the disjunctive normal form, where □k(k ≥ 0) only occurs before an atomic formula p, and $\lnot$ only occurs before a pseudo-atomic formula of form □k p. Maximally consistent sets of K +  have a property holding in the propositional logic: a set of pseudo-atom-complete formulas uniquely determines a maximally consistent set. When a pseudo-atomic formula □k pi (k,i ≥ 0) is corresponding to a propositional variable qki, each formula in K +  then can be corresponding to a formula in the propositional logic P + . We can also get the correspondence of models between K +  and P + . Then we get correspondences of theorems and valid formulas between them. So, the soundness theorem and the completeness theorem of K +  follow directly from those of P +