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The class of finitary normal logic programs—identified recently, in [1]—makes it possible to reason effectively with function symbols, recursion, and infinite stable models. These features may lead to a full integration of the standard logic programming paradigm with the answer set programming paradigm. For all finitary programs, ground goals are decidable, while nonground goals are semidecidable...
We study algorithms for computing stable models of propositional logic programs and derive estimates on their worst-case performance that are asymptotically better than the trivial bound of O(m2n), where m is the size of an input program and n is the number of its atoms. For instance, for programs, whose clauses consist of at most two literals (counting the head) we design an algorithm to compute...
Answer set programming has emerged as a new important paradigm for declarative problem solving. It relies on algorithms that compute the stable models of a logic program, a problem that is, in the worst-case, intractable. Although, local search procedures have been successfully applied to a variety of hard computational problems, the idea of employing such procedures in answer set programming has...
We present a modification of Brass et al’s transformation-based method for the bottom-up computation of well-founded semantics (WFS), in order to cope with explicit negation, in the sense of Alferes and Pereira’s WFSX semantics. This variation consists in the simple addition of two intuitive transformations that guarantee the satisfaction of the socalled coherence principle: whenever an objective...
Defeasible reasoning is a simple but efficient approach to nonmonotonic reasoning that has recently attracted considerable interest and that has found various applications. Defeasible logic and its variants are an important family of defeasible reasoning methods. So far no relationship has been established between defeasible logic and mainstream nonmonotonic reasoning approaches. In this paper...
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. 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...
In this experience paper we present a case study in using logic programming in a pervasive computing project in the healthcare domain. An expert system is used to detect healthcare activities in a pervasive hospital environment where positions of people and things are tracked. Based on detected activities an activity-driven computing infrastructure provides computational assistance to healthcare staff...
Current trends in Software Engineering and developments in Logic Programming lead us to believe that there will be an opportunity for Logic Programming to make a breakthrough in Software Engineering. In this paper, we explain how this has arisen, and justify our belief with a real-life application. Above all, we invite fellow workers to take up the challenge that the opportunity offers.
The paper introduces the SILK tool-set, a tool-set based on constraint logic programming techniques for the support of application integration. We focus on the Integrator component of SILK, which provides tools and techniques to support the process of model evolution: unification of the models of the information sources and their mapping onto the conceptual models of their user-groups. We present...
It becomes more and more important to discover knowledge in massive information. The knowledge can be taken as a theory. As the information increases, the theories should be updated. Thus we get a sequence of theories, denoted by Π1, Π2,..., Πn,.... This procedure may never stop, i.e. maybe there is not a natural number k such that Πk = Π...
A neural implementation which provides an interesting massively parallel model for computing a fixed-point semantics of a program is introduced for multiadjoint logic programming [3]. Distinctive features of this programming paradigm are that: very general aggregation connectives in the bodies are allowed; by considering different adjoint pairs, it is possible to use several implications in the rules.
The result of introducing Fuzzy Logic into Logic Programming has been the development of several “Fuzzy Prolog” systems. These systems replace the inference mechanism of Prolog with a fuzzy variant which is able to handle partial truth as a real value or as an interval on [0,1]. Most of these systems consider only one operator to propagate the truth value through the fuzzy rules. We aim at...
CLP(FD) programs can solve complex problems but they are difficult to develop and maintain. In particular, their operational behavior is not easy to understand. Execution tracers can give some insight of executions, but they are mapped onto the operational semantics of the language. This, in general, is a too low-level picture of the execution. In particular, application developers and end-users do...
This paper presents an application of higher-order logic programming: program schemata and schema-based transformations of logic programs. We are constructing higher-order programs that can unify logic programs with suitable program schemata, which are also higher-order constructs. They are abstracting out common recursive control flow patterns, and we can think about logic programs as about instances...
Many frameworks have been proposed for the management of uncertainty in logic programs (see, e.g. [1] for a list of references). Roughly, they can be classified into annotation based (AB) and implication based (IB) approaches. In the AB approach, a rule has form A: f(β1,..., βn) ←B1:β1,..., Bn:βn, asserting “the certainty...
We propose a new way of extending Logic Programming (LP) for reasoning with uncertainty. Probabilistic finite domains (Pfd) capitalise on ideas introduced by Constraint LP, on how to extend the reasoning capabilities of the LP engine. Unlike other approaches to the field, Pfd syntax can be intuitively related to the axioms defining Probability and to the underlying concepts of Probability Theory,...
Reactive systems are those that continuously interact with their environment asynchronously. A number of formalisms have been presented in the literature for reactive systems. However, these formalisms do not model systems that consist of a number of reactive sub-components dynamically interacting with each other and the environment. An example of this type of system can be seen in the telecommunications...
Prolog has been used as an inference engine of many systems, and it is natural to use Prolog as an inference engine of intelligent agent systems. However, Prolog assumes that a program does not change. This poses a problem because the agent might work in a dynamic environment where unexpected things can happen. In order to use a Prolog-like procedure as an inference engine of an agent, the procedure...
We provide here a declarative and model-theoretic characterization of the approximations computed by consistency during the resolution of finite domain constraint satisfaction problems.
This communication is a continuation of our previous work on the TCLP type system for constraint logic programming [1]. Here we introduce overloading in TCLP and describe a new implementation of TCLP in the Constraint Handling Rules language CHR. Overloading, that is assigning several types to symbols, e.g. for integer and floating point arithmetic, makes it possible to avoid subtype relations like...
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