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The PITA system: Tabling and answer subsumption for reasoning under uncertainty

theory and practice of logic programming 2011年第4-5期11卷 433-449页

作者： Riguzzi, Fabrizio Swift, Terrance Univ Ferrara ENDIF I-44122 Ferrara Italy Univ Nova Lisboa CENTRIA P-1200 Lisbon Portugal

Many real world domains require the representation of a measure of uncertainty. The most common such representation is probability, and the combination of probability with logic programs has given rise to the field of Probabilistic logic programming (PLP), leading to languages such as the Independent Choice logic, logic Programs with Annotated Disjunctions (LPADs), Problog, PRISM, and others. These languages share a similar distribution semantics, and methods have been devised to translate programs between these languages. The complexity of computing the probability of queries to these general PLP programs is very high due to the need to combine the probabilities of explanations that may not be exclusive. As one alternative, the PRISM system reduces the complexity of query answering by restricting the form of programs it can evaluate. As an entirely different alternative, Possibilistic logic Programs adopt a simpler metric of uncertainty than probability. Each of these approaches-general PLP, restricted PLP, and Possibilistic logic programming-can be useful in different domains depending on the form of uncertainty to be represented, on the form of programs needed to model problems, and on the scale of the problems to be solved. In this paper, we show how the PITA system, which originally supported the general PLP language of LPADs, can also efficiently support restricted PLP and Possibilistic logic Programs. PITA relies on tabling with answer subsumption and consists of a transformation along with an API for library functions that interface with answer subsumption. We show that, by adapting its transformation and library functions, PITA can be parameterized to PITA(IND,EXC) which supports the restricted PLP of PRISM, including optimizations that reduce non-discriminating arguments and the computation of Viterbi paths. Furthermore, we show PITA to be competitive with PRISM for complex queries to Hidden Markov Model examples, and sometimes much faster. We further show

关键词： Probabilistic logic programming Possibilistic logic programming Tabling Answer Subsumption Program Transformation

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Splitting and updating hybrid knowledge bases

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theory and practice of logic programming 2011年第4-5期11卷 801-819页

作者： Slota, Martin Leite, Joao Swift, Terrance Univ Nova Lisboa CENTRIA P-2829516 Caparica Portugal Univ Nova Lisboa Dept Informat P-2829516 Caparica Portugal

Over the years, nonmonotonic rules have proven to be a very expressive and useful knowledge representation paradigm. They have recently been used to complement the expressive power of Description logics (DLs), leading to the study of integrative formal frameworks, generally referred to as hybrid knowledge bases, where both DL axioms and rules can be used to represent knowledge. The need to use these hybrid knowledge bases in dynamic domains has called for the development of update operators, which, given the substantially different way DLs and rules are usually updated, has turned out to be an extremely difficult task. In Slota and Leite (2010b Towards Closed World Reasoning in Dynamic Open Worlds. theory and practice of logic programming, 26th Int'l. Conference on logic programming (ICLP'10) Special Issue 10(4-6) (July), 547-564.), a first step towards addressing this problem was taken, and an update operator for hybrid knowledge bases was proposed. Despite its significance-not only for being the first update operator for hybrid knowledge bases in the literature, but also because it has some applications-this operator was defined for a restricted class of problems where only the ABox was allowed to change, which considerably diminished its applicability. Many applications that use hybrid knowledge bases in dynamic scenarios require both DL axioms and rules to be updated. In this paper, motivated by real world applications, we introduce an update operator for a large class of hybrid knowledge bases where both the DL component as well as the rule component are allowed to dynamically change. We introduce splitting sequences and splitting theorem for hybrid knowledge bases, use them to define a modular update semantics, investigate its basic properties, and illustrate its use on a realistic example about cargo imports.

关键词： Hybrid knowledge base Update Splitting theorem Ontology logic program

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Observational equivalences for linear logic concurrent constraint languages

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theory and practice of logic programming 2011年第4-5期11卷 469-485页

作者： Haemmerle, Remy Tech Univ Madrid Madrid Spain

Linear logic Concurrent Constraint programming (LCC) is an extension of concurrent constraint programming (CC), where the constraint system is based on Girard's linear logic instead of the classical logic. In this paper, we address the problem of program equivalence for this programming framework. For this purpose, we present a structural operational semantics for LCC based on a label transition system and investigate different notions of observational equivalences inspired by the state of art of process algebras. Then, we demonstrate that the asynchronous pi-calculus can be viewed as simple syntactical restrictions of LCC. Finally, we show that LCC observational equivalences can be transposed straightforwardly to classical Concurrent Constraint languages and Constraint Handling Rules, and investigate the resulting equivalences.

关键词： Concurrent Constraint programming linear logic observational equivalences bisimulation pi-calculus Constraint Handling Rules

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Optimal placement of valves in a water distribution network with CLP(FD)

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theory and practice of logic programming 2011年第4-5期11卷 731-747页

作者： Cattafi, Massimiliano Gavanelli, Marco Nonato, Maddalena Alvisi, Stefano Franchini, Marco Univ Ferrara Dept Engn I-44122 Ferrara Italy

This paper presents a new application of logic programming to a real-life problem in hydraulic engineering. The work is developed as a collaboration of computer scientists and hydraulic engineers, and applies Constraint logic programming to solve a hard combinatorial problem. This application deals with one aspect of the design of a water distribution network, i.e., the valve isolation system design. We take the formulation of the problem by Giustolisi and Savic (2008 Optimal design of isolation valve system for water distribution networks. In Proceedings of the 10th Annual Water Distribution Systems Analysis Conference WDSA2008, J. Van Zyl, A. Ilemobade, and H. Jacobs, Eds.) and show how, thanks to constraint propagation, we can get better solutions than the best solution known in the literature for the Apulian distribution network. We believe that the area of the so-called hydroinformatics can benefit from the techniques developed in Constraint logic programming and possibly from other areas of logic programming, such as Answer Set programming.

关键词： constraint logic programming hydraulic engineering valve placement graph partitioning

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Actual causation in CP-logic

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theory and practice of logic programming 2011年第4-5期11卷 647-662页

作者： Vennekens, Joost Lessius Mechelen Mechelen Belgium

Given a causal model of some domain and a particular story that has taken place in this domain, the problem of actual causation is deciding which of the possible causes for some effect actually caused it. One of the most influential approaches to this problem has been developed by Halpern and Pearl (Halpern, J. and Pearl, J. 2005. Causes and explanations: A structural-model approach. Part I: Causes. British Journal for the Philosophy of Science 56 (4), 843-887) in the context of structural models. In this paper, I argue that this is actually not the best setting for studying this problem. As an alternative, I offer the probabilistic logic programming language of CP-logic. Unlike structural models, CP-logic incorporates the deviant/default distinction that is generally considered an important aspect of actual causation, and it has an explicitly dynamic semantics, which helps to formalize the stories that serve as input to an actual causation problem.

关键词： Semantics

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The magic of logical inference in probabilistic programming

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theory and practice of logic programming 2011年第4-5期11卷 663-680页

作者： Gutmann, Bernd Thon, Ingo Kimmig, Angelika Bruynooghe, Maurice De Raedt, Luc Katholieke Univ Leuven Dept Comp Sci B-3001 Heverlee Belgium

Today, there exist many different probabilistic programming languages as well as more inference mechanisms for these languages. Still, most logic programming-based languages use backward reasoning based on Selective Linear Definite resolution for inference. While these methods are typically computationally efficient, they often can neither handle infinite and/or continuous distributions nor evidence. To overcome these limitations, we introduce distributional clauses, a variation and extension of Sato's distribution semantics. We also contribute a novel approximate inference method that integrates forward reasoning with importance sampling, a well-known technique for probabilistic inference. In order to achieve efficiency, we integrate two logic programming techniques to direct forward sampling. Magic sets are used to focus on relevant parts of the program, while the integration of backward reasoning allows one to identify and avoid regions of the sample space that are inconsistent with the evidence.

关键词： probabilistic logic forward reasoning sampling continuous distributions

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Guarded resolution for Answer Set programming

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theory and practice of logic programming 2011年第1期11卷 111-123页

作者： Marek, V. W. Remmel, J. B. Univ Kentucky Dept Comp Sci Lexington KY 40506 USA Univ Calif San Diego Dept Math La Jolla CA 92903 USA Univ Calif San Diego Dept Comp Sci La Jolla CA 92903 USA

We investigate a proof system based on a guarded resolution rule and show its adequacy for the stable semantics of normal logic programs. As a consequence, we show that Gelfond-Lifschitz operator can be viewed as a proof-theoretic concept. As an application, we find a propositional theory E-p whose models are precisely stable models of programs. We also find a class of propositional theories C-P with the following properties. Propositional models of theories in C-P are precisely stable models of P, and the theories in C-T are of the size linear in the size of P.

关键词： guarded resolution proof-theory for Answer Set programming

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Non-termination analysis of logic programs with integer arithmetics

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theory and practice of logic programming 2011年第4-5期11卷 521-536页

作者： Voets, Dean De Schreye, Danny Katholieke Univ Leuven Dept Comp Sci B-3001 Heverlee Belgium

In the past years, analyzers have been introduced to detect classes of non-terminating queries for definite logic programs. Although these non-termination analyzers have shown to be rather precise, their applicability on real-life Prolog programs is limited because most Prolog programs use non-logical features. As a first step towards the analysis of Prolog programs, this paper presents a non-termination condition for logic Programs containing integer arithmetics. The analyzer is based on our non-termination analyzer presented at International logic programming Conference (ICLP) 2009. The analysis starts from a class of queries and infers a subclass of non-terminating ones. In first phase, we ignore the outcome (success or failure) of the arithmetic operations, assuming success of all arithmetic calls. In second phase, we characterize successful arithmetic calls as a constraint problem, the solution of which determines the non-terminating queries.

关键词： non-termination analysis numerical computation constraint-based approach

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Modular architecture with microcontroller for advanced electronic practices

Modular architecture with microcontroller for advanced elect...

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Technologies Applied to Electronics Teaching (TAEE)

作者： Javier Diz J. Fernando Garcia Jorge Dominguez Department Electronics IES Escolas Proval Nigran Spain

The high level of complexity of integrated circuits is one of the main problems in modern electronic practices. These circuits can only be explained on a theoretical level or require expensive and specialized equipment. The traditional teaching of electronics based on discrete components or LSI integrated circuits as logic gates or flip-flops is being clearly outdated, and runs the risk of creating a gap between theory and practice that goes against the spirit of professional training. This article presents a hardware and software set of components designed for advanced electronic practices whose centerpiece is a microcontroller that connects different peripherals such as analog-to-digital converters, keyboards, displays of different technologies (including latest graphics LCD modules), power and different communications interfaces and protocols. This modular architecture can be used in basic training modules (such as analog and digital electronics) but also in more specific modules such as sound, home automation, robotics and industrial control. The components used are cheap and modules can be built in the schools to reduce its cost. The schematics and printed circuit boards are free to use and for their design has been used the open source program Kicad. The microcontroller programming environment is based on Eclipse-SDCC, which is also open source and multiplatform. This system can be used for demonstrations and school practices. The system can also be used as a platform for teaching C programming or assembler for microcontrollers. All the elements have been developed at the institute "Escolas Proval" of Nigrán (Pontevedra) by a team of electronics teachers and students. Over the last years have been designed and built some of the modules and it is planned to continue making new ones based on the training needs that will be detected and new professional qualifications currently under implementation.

关键词： Microcontrollers programming profession Power supplies Robots Connectors Education

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Complex optimization in answer set programming

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theory and practice of logic programming 2011年第4-5期11卷 821-839页

作者： Gebser, Martin Kaminski, Roland Schaub, Torsten Univ Potsdam Inst Informat Potsdam Germany Simon Fraser Univ Burnaby BC V5A 1S6 Canada Griffith Univ Nathan Qld 4111 Australia

Preference handling and optimization are indispensable means for addressing nontrivial applications in Answer Set programming (ASP). However, their implementation becomes difficult whenever they bring about a significant increase in computational complexity. As a consequence, existing ASP systems do not offer complex optimization capacities, supporting, for instance, inclusion-based minimization or Pareto efficiency. Rather, such complex criteria are typically addressed by resorting to dedicated modeling techniques, like saturation. Unlike the ease of common ASP modeling, however, these techniques are rather involved and hardly usable by ASP laymen. We address this problem by developing a general implementation technique by means of meta-prpogramming, thus reusing existing ASP systems to capture various forms of qualitative preferences among answer sets. In this way, complex preferences and optimization capacities become readily available for ASP applications.

关键词： Answer Set programming Preference Handling Complex optimization Meta-programming

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