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Nomenclatura Unesco > (11) Lógica

Mostrando recursos 110,721 - 110,740 de 146,115

110721. Constraint Systems for Pattern Analysis of Constraint Logic-Based Languages - Roberto Bagnara
Pattern analysis consists in determining the shape of the set of solutions of the constraint store at some program points. Our basic claim is that pattern analyses can all be described within a unified framework of constraint domains. We show the basic blocks of such a framework as well as construction techniques which induce a hierarchy of domains. In particular, we propose a general methodology for domain combination with asynchronous interaction. The interaction among domains is asynchronous in that it can occur at any time: before, during, and after the product operation in a completely homogeneous way. That is achieved by regarding semantic domains as particular kinds...

110722. Using Reconfigurable Processors as Control System Elements - Timo Korhonen,Adrian Lawrence,Junji Urakawa
A control system applying reconfigurable computers has been designed and built for the active alignment system of ATF at KEK. The system measures the relative position of accelerator components with a high precision allowing remote correction of the misalignments. A control system that acquires the data and permits the position control was developed. The system was built using reconfigurable logic as processing elements. To program the devices, a hardware compiler was utilized. The system structure, divided into functional levels and the tasks and processings done at each level is reported. 1 Introduction The ATF (Accelerator Test Facility) at KEK has been built with the purpose of studying the techniques and phenomena related to building...

110723. The Control System for a 2 MeV Tandem Accelerator used for Contraband Detection - D. Dale,D. Bishop,H. Hui,B. Milton,B. Roberts
The Contraband Detection System (CDS) is a system designed for detection of explosives and other contraband utilizing Gamma Resonance Absorption (GRA). In the CDS 9.17 MeV gammas are produced by 1.75 MeV protons interacting with a Carbon 13 target. The 2 MeV Tandem is capable of producing upto 10mA of C.W. proton beam. The Control System consists of two AllenBradley SLC500 series Programmable Logic Controllers (PLC). One resides at ground potential and the other is located inside the Tandem pressure vessel at 1 MegaVolt. Supervisory control and communication between the two PLCs is accomplished using the Allen-Bradley Data Highway Plus and fiber optics. Operation of the system is described. 1 Introduction TRIUMF and Northrop Grumman...

110724. Electronic Newsletter On Reasoning About Actions And Change
this paper is to examine what the competition tells us about logic and its role in planning. Logic and logical approaches have long been criticized as been computationally ineffective, yet some of the best performing planners in the competition were based on logic. So it would seem that there is reason for researchers in logic-based AI to be optimistic.

110725. A Guide to SNARK - Mark E. Stickel,Richard J. Waldinger,Vinay K. Chaudhri
This document is an example-driven tutorial introduction to snark that will allow the reader to experiment with the system. It does not purport 1 PREFACE 5 to introduce mathematical logic or resolution theorem proving; [Chang] provides an introduction to this style of theorem proving that does not assume any prior knowledge of logic. The guide also uses some notions introduced more fully in [Manna] and [Waldinger], particularly nonclausal resolution, quantifier force, and answer extraction. Knowledge of lisp syntax and basics is also assumed here (e. g., see [Graham] or [Pitman]). Nevertheless, it is intended that a reader who is willing to suspend incomprehension will be able to read this document...

110726. Sharing Revisited - Roberto Bagnara,Patricia M. Hill,Enea Zaanella
Although the usual goal of sharing analysis is to detect which pairs of variables share, the standard choice for sharing analysis is a domain that characterizes setsharing. In this paper, we question, apparently for the first time, whether this domain is over-complex for pair-sharing analysis. We show that the answer is yes. By defining an equivalence relation over the set-sharing domain we obtain a simpler domain, reducing the complexity of the abstract unification procedure. We present preliminary experimental results, showing that, in practice, our domain compares favorably with the set-sharing one over a wide range of benchmark programs. 1 Introduction In logic programming, a knowledge of sharing between variables...

110727. Using Multi-Context Systems to Engineer Executable Agents
In the area of agent-based computing there are many proposals for specific system architectures, and a number of proposals for general approaches to building agents. As yet, however, there are few attempts to relate these together, and even fewer attempts to provide methodologies which relate designs to architectures and then to executable agents. This paper provides a first attempt to address this shortcoming; we propose a general method of defining architectures for logic-based agents which can be directly executed. Our approach is based upon the use of multi-context systems and we illustrate its use with an example architecture capable of argumentation-based negotiation. 1 Introduction Agent-based computing is fast emerging as a...

110728. Complexity of Fuzzy Probability Logics - Petr H Ajek,Sauro Tulipani
. The satisfiability problem for the logic FP(L/) (fuzzy probability logic over L/ukasiewicz logic) is shown to be NP-complete; satisfiability in FP(L/#) (the same over the logic joining L/ukasiewicz and product logic) is shown to be in PSPACE. Keywords: a list of a few keywords 1. Introduction It has been repeatedly stressed by many authors that truth values in fuzzy logic must be strictly distinguished from any probabilities, if fuzzy logic is understood (as it usually is) truth-functional; probability is not truth-functional. Nevertheless, one can build calculi of fuzzy logic speaking in a fuzzy way on probabilities (see[7, 6]). The main approach is to take the probability of...

110729. The Effect of Syntactic Form on Simple Belief Revisions and Updates - Rene Elio,Francis Jeffry Pelletier
In this paper we report preliminary results on how people revise or update a previously held set of beliefs. When intelligent agents learn new things which conflict with their current belief set, they must revise their belief set. When the new information does not conflict, they merely must update their belief set. Various AI theories have been proposed to achieve these processes. There are two general dimensions along which these theories differ: whether they are syntactic-based or model-based, and what constitutes a minimal change of beliefs. This study investigates how people update and revise semantically equivalent but syntactically distinct belief sets, both in symbolic-logic problems and in quasi-real-world problems. Results indicate that syntactic...

110730. Natural Language Multiprocessing: A Case Study - Enrico Pontelli,Gopal Gupta,Janyce Wiebe,David Farwell
This paper presents two case studies of parallelization of large Natural Language Processing (NLP) applications using a parallel logic programming system (called "ACE") that automatically exploits implicit parallelism. The first system considered is Artwork, a system for semantic disambiguation, speech act resolution, and temporal reference resolution. The second system is ULTRA, a multilingual translation system. Both applications were originally developed in Prolog without any consideration for parallel processing. The results obtained confirm that NLP is a ripe area for exploitation of parallelism. Most previous work on parallelism in NLP focused primarily on parallelizing the parsing phase of language processing. The...

110731. A Stochastic Model of Actions and Plans for Anytime Planning under Uncertainty - Joachim Hertzberg,Informatik Viii,William Shoaff,Moti Schneider,Tom Gordon,Gerd Grosse,Eric Jacopin,Jurgen Paulokat,Eric Rutten,Josef Schneeberger
Building planning systems that operate in real domains requires coping with both uncertainty and time pressure. This paper describes a model of reaction plans, which are generated using a formalization of actions and of state descriptions in probabilistic logic, as a basis for anytime planning under uncertainty. The model has the following main features. At the action level, we handle incomplete and ambiguous domain information, and reason about alternative action effects whose probabilities are given. On this basis, we generate reaction plans that specify different courses of action, reflecting the domain uncertainty and alternative action effects; if generation time was insufficient, these plans may be left unfinished, but...

110732. A hierarchy of Constraint Systems for Data-Flow Analysis of Constraint Logic-Based Languages - Roberto Bagnara
Many interesting analyses for constraint logic-based languages are aimed at the detection of monotonic properties, that is to say, properties that are preserved as the computation progresses. Our basic claim is that most, if not all, of these analyses can be described within a unified notion of constraint domains. We present a class of constraint systems that allows for a smooth integration within an appropriate framework for the definition of non-standard semantics of constraint logic-based languages. Such a framework is also presented and motivated. We then show how such domains can be built, as well as construction techniques that induce a hierarchy of domains with interesting properties. In...

110733. On Policy-based Extensible Hierarchical Network Management in QoS-enabled IP Networks - P. Flegkas,P. Trimintzios,G. Pavlou,I. Andrikopoulos,C. F. Cavalcanti
Policy-based Management has been the subject of extensive research over the last decade. More recently, the IETF has been investigating Policy-based Networking as a means for managing IP-based multi-service networks with quality of service guarantees. Policies are seen as a way to guide the behaviour of a network or distributed system through high-level, declarative directives. We mainly view policies as a means of extending the logic of a management system at runtime, so that it can be adaptive to changing or newly emerging requirements. We are interested in particular in the coexistence of "hard-wired" hierarchical management systems with policy logic...

110734. The Implementation of Lazy Narrowing - Manuel M. T. Chakravarty,Hendrik C. R. Lock,Vincenz Prienitz Strae
Lazy narrowing has been proposed as the operational model of functional logic languages. This paper presents a new abstract machine which implements lazy narrowing. The core of this machine consists of a conventional stack based architecture like the one used for imperative languages. Almost orthogonal extensions of this core implement the different concepts of functional logic languages. This simplifies the machine design to a great deal and reduces the instruction set which has been particularly designed to support the application of standard code generation techniques. By its orthogonality, it is achieved that unused features introduce only minimal overhead. As a result, when performing ground term reduction the...

110735. Factorizing Equivalent Variable Pairs in ROBDD-Based Implementations of Pos - Roberto Bagnara
. The subject of groundness analysis for (constraint) logic programs has been widely studied, and interesting domains have been proposed. Pos has been recognized as the most suitable domain for capturing the kind of dependencies arising in groundness analysis, and Reduced Ordered Binary Decision Diagrams (ROBDDs) are generally accepted to be the most efficient representation for Pos. Unfortunately, the size of an ROBDDs is, in the worst case, exponential in the number of variables it depends upon. Earlier work [2] has shown that a hybrid representation that separates the definite information from the dependency information is considerably more efficient than keeping the two together. The aim of the present paper...

110736. Set-Sharing is Redundant for Pair-Sharing - Roberto Bagnara,Patricia M. Hill,Enea Zaanella
. Although the usual goal of sharing analysis is to detect which pairs of variables share, the standard choice for sharing analysis is a domain that characterizes set-sharing. In this paper, we question, apparently for the first time, whether this domain is over-complex for pair-sharing analysis. We show that the answer is yes. By defining an equivalence relation over the set-sharing domain we obtain a simpler domain, reducing the complexity of the abstract unification procedure. We present preliminary experimental results, showing that, in practice, our domain compares favorably with the set-sharing one over a wide range of benchmark programs. 1 Introduction In logic programming, a knowledge of sharing between variables...

110737. Comparison of Technology-Based and State-Based Representations for the Synthesis of Synchronous Sequential Logic from Partial Input-Output Sequence - Chaiyasit Manovit,Chatchawit Aporntewan,Prabhas Chongstitvatana
This paper compares the computational efforts of synchronous sequential logic circuit synthesis from partial input-output sequence by Genetic Algorithm (GA) using different representations; technology-based and state-based. The state-based representation is technology independent. It can be further optimized and benefits from exising synthesis and optimization techniques which work with finite state machines. The resulting state transition diagram can be implemented in any Programmable Logic Device using vendors's CAD tools. The technology-based representation, in this experiment, is a registered PAL device. The result shows, however, that the state-based approach requires greater effort than that of technology-based approach when we permit the same...

110738. Soundness, Idempotence and Commutativity of Set-Sharing - Patricia M,Roberto Bagnara,Enea Zaffanella
It is important that practical data-flow analyzers are backed by reliably proven theoretical results. Abstract interpretation provides a sound mathematical framework and necessary generic properties for an abstract domain to be well-defined and sound with respect to the concrete semantics. In logic programming, the abstract domain Sharing is a standard choice for sharing analysis for both practical work and further theoretical study. In spite of this, we found that there were no satisfactory proofs for the key properties of commutativity and idempotence that are essential for Sharing to be well-defined and that published statements of the soundness of Sharing assume the occurs-check. This paper provides a generalization of...

110739. Static Analysis of CLP Programs over Numeric Domains - Roberto Bagnara,Roberto Giacobazzi,Giorgio Levi
Constraint logic programming (CLP) is a generalization of the pure logic programming paradigm, having similar model-theoretic, fixpoint and operational semantics [9]. Since the basic operational step in program execution is a test for solvability of constraints in a given algebraic structure, CLP has in addition an algebraic semantics. CLP is then a general paradigm which may be instantiated on various semantic domains, thus achieving a good expressive power. One relevant feature is the distinction between testing for solvability and computing a solution of a given constraint formula. In the logic programming case, this corresponds to the unification process, which tests for solvability by computing a solution (a set of...

110740. Factorizing Equivalent Variable Pairs in ROBDD-Based Implementations of Pos - Roberto Bagnara,Peter Schachte
The subject of groundness analysis for (constraint) logic programs has been widely studied, and interesting domains have been proposed. Pos has been recognized as the most suitable domain for capturing the kind of dependencies arising in groundness analysis, and Reduced Ordered Binary Decision Diagrams (ROBDDs) are generally accepted to be the most efficient representation for Pos. Unfortunately, the size of an ROBDDs is, in the worst case, exponential in the number of variables it depends upon. Earlier work [2] has shown that a hybrid representation that separates the definite information from the dependency information is considerably more efficient than keeping...

 

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