Results 1 
6 of
6
Constructive Negation Without Subsidiary Trees
 of LSI Department, Univ. Politécnica de Catalunya
, 2000
"... In this paper we propose a new operational semantics, called BCN, which is sound and complete with respect to ClarkKunen'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 Co ..."
Abstract

Cited by 4 (2 self)
 Add to MetaCart
In this paper we propose a new operational semantics, called BCN, which is sound and complete with respect to ClarkKunen'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 metarule. Second, the way in which BCN is defined makes it an extensible scheme to NCLP over arbitrary constraint domains. 1
Tight and Loose Semantics for Transformation Systems
 Recent Trends in Algebraic Development Techniques, Springer LNCS 2267 (2001
, 2001
"... Abstract. When defining the requirements of a system, specification units typically are partial or incomplete descriptions of a system component. In this context, providing a complete description of a component means integrating all the existing partial views for that component. However, in many cas ..."
Abstract

Cited by 2 (1 self)
 Add to MetaCart
Abstract. When defining the requirements of a system, specification units typically are partial or incomplete descriptions of a system component. In this context, providing a complete description of a component means integrating all the existing partial views for that component. However, in many cases defining the semantics of this integration operation is not an easy task. In particular, this is the case when the framework used at the specification level is, in some sense, an “operational ” one (e.g. a Petri net or a statechart). Moreover, this problem may also apply to the definition of compositional semantics for modular constructs for this kind of frameworks. In this paper, we study this problem, at a general level. First, we define a general notion of framework whose semantics is defined in terms of transformations over states represented as algebras and characterize axiomatically the standard tight semantics. Then, inspired in the doublepullback approach defined for graph transformation, we axiomatically present a loose semantics for this class of transformation systems, exploring their compositional properties. In addition, we see how this approach may be applied to a number of formalisms. 1
A Functorial Framework for Constraint Normal Logic Programming
"... Abstract. The semantic constructions and results for definite programs do not extend when dealing with negation. The main problem is related to a wellknown problem in the area of algebraic specification: if we fix a constraint domain as a given model, its free extension by means of a set of Horn cl ..."
Abstract

Cited by 1 (0 self)
 Add to MetaCart
Abstract. The semantic constructions and results for definite programs do not extend when dealing with negation. The main problem is related to a wellknown problem in the area of algebraic specification: if we fix a constraint domain as a given model, its free extension by means of a set of Horn clauses defining a set of new predicates is semicomputable. However, if the language of the extension is richer than Horn clauses its free extension (if it exists) is not necessarily semicomputable. In this paper we present a framework that allows us to deal with these problems in a novel way. This framework is based on two main ideas: a reformulation of the notion of constraint domain and a functorial presentation of our semantics. In particular, the semantics of a logic program P is defined in terms of three functors: (OP P,ALG P,LOG P) that apply to constraint domains and provide the operational, the least fixpoint and the logical semantics of P, respectively. To be more concrete, the idea is that the application of OP P to a specific constraint solver, provides the operational semantics of P that uses this solver; the application of ALG P to a specific domain, provides the least fixpoint of P over this domain; and, the application of LOG P to a theory of constraints, provides the logic theory associated to P. In this context, we prove that these three functors are in some sense equivalent. 1
A Generalization of the Folding Rule for the ClarkKunen Semantics ⋆
"... Abstract. In this paper, we propose more flexible applicability conditions for the folding rule that increase the power of existing unfold/fold systems for normal logic programs. Our generalized folding rule enables new transformation sequences that, in particular, are suitable for recursion introdu ..."
Abstract
 Add to MetaCart
Abstract. In this paper, we propose more flexible applicability conditions for the folding rule that increase the power of existing unfold/fold systems for normal logic programs. Our generalized folding rule enables new transformation sequences that, in particular, are suitable for recursion introduction and local variable elimination. We provide some illustrative examples and give a detailed proof of correctness w.r.t. the ClarkKunen semantics. 1