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Nomenclatura Unesco > (11) Lógica

Mostrando recursos 110,721 - 110,740 de 132,440

110721. IEC 1131-3 and the Instruction List Language
This article is about the weaknesses of part 3 of the IEC 1131 standard and in particular of one of the languages it defines called Instruction List. It will also propose ways to improve the standard so that it can be used to create high quality software. 1 Introduction Traditionally when some control circuit was needed in for example a chemical plant, it would be implemented using hardwired logic, i.e. a hardware circuit consisting of AND and NAND gates. Unfortunately hardware circuits are inherently inflexible. The software implementation of Boolean functions, called programmed logic, is much more flexible. Programmed logic uses a processor with memory for a program, memory...

110722. Experiences with a mechanisation of Martin-Lof's Theory of Types - Gustavo Betarte
Martin-Lof's Theory of Types-MLTT- can be used as a logical framework in which other theories can be defined. This paper describes ILF, a mechanisation of MLTT which allows definition of object theories, judgement checking, reduction of expressions and other facilities for its use. An example of how a particular object theory - Martin-Lof's Monomorphic Theory of Sets - can be defined in ILF and used to develop correct programs is also presented. Keywords : Logical Framework, Programming Logic, Martin-Lof's Theory of Types. Both authors are partially supported by a PEDECIBA (Programa de Desarrollo de las Ciencias B'asicas) grant. 1 Introduction. During the last two decades, as direct result...

110723. An Overview of Hybrid Systems - N. B. O. L. Pettit
"Hybrid systems" is a term that has recently started to appear with some frequency at control conferences, with sessions dedicated to the topic and a workshop specifically for the subject. This report tries to give a flavour of what people mean when talking about hybrid systems. It will also try and assess whether there is any useful application technology that might result from this research. Much of the material comes from an invited workshop held on Block Island in September 1995. The proceedings from this are now in print as a Springer Verlag monograph, "Control using Logic-Based Switching" edited by S. Morse. 1 now at CF-T, Danfoss A/S, 6430...

110724. STDL A Portable Language for Transaction Processing - Philip A. Bernstein,Per O. Gyllstrom,Tom Wimberg
This paper describes STDL's transaction features: transaction bracketing, transactional remote procedure call, transactional queuing, recoverable terminal I/O, and transactional exception handling. STDL relies on standard C and COBOL for most application logic and all operations on SQL databases and files. All transactional features of STDL and new features outside standard C and COBOL are isolated in procedures written in the STDL language. These procedures are called tasks. This isolation of transactional features is quite different than other persistent programming languages: one can use applications written in standard C or COBOL; and to implement STDL, it is possible to map clauses of task language onto operations of most any distributed TP monitor. Keywords: transactions,...

110725. Generating Declarative Language Bias for Top-Down ILP Algorithms - Stefan Kramer
Many of today's algorithms for Inductive Logic Programming (ILP) put a heavy burden and responsibility on the user, because their declarative bias have to be defined in a rather low-level fashion. To address this issue, we developed a method for generating declarative language bias for top-down ILP systems from high-level declarations. The key feature of our approach is the distinction between a user level and an expert level of language bias declarations. The expert provides abstract meta-declarations, and the user declares the relationship between the meta-level and the given database to obtain a low-level declarative language bias. The suggested languages allow for compact and abstract specifications of the declarative language...

110726. Formalisation of Anaesthesiology for Decision Support - Gerard R. Renardel De Lavalette,Rix Groenboom,Ernest Rotterdam,Frank Van Harmelen,Annette Ten Teije,Fred De Geus
This paper reports on research for decision support for anaesthesiologists at the University Hospital in Groningen, the Netherlands. Based on Carola, an existing automated operation documentation system, we design a support environment that will assist in real-time diagnosis. The core of the work presented here consists of a knowledge base (containing anaesthesiological knowledge) and a diagnosis system. The knowledge base is specified in the logic-based formal specification language AFSL. This leads to a powerful and precise treatment of knowledge structuring and data abstraction. Keywords anaesthesiology, formalisation of knowledge, data abstraction, diagnostic reasoning 1 Introduction We report in this paper on the research project FAN (Formalisation of ANaesthesiology) . FAN aims to contribute...

110727. Evaluating an Algorithm for Default Reasoning - Ilkka Niemel,Patrik Simons
In this paper performance of a lately proposed decision procedure for Reiter's default logic is evaluated. Recent complexity results indicate that there are two orthogonal sources of complexity in default reasoning: classical (ørstorder) reasoning and conAEict resolution (i.e. choosing an appropriate set of applicable nonconAEicting default rules). For classical reasoning well-known techniques exist and conAEict resolution presents the new computational challenge in default reasoning. However, ef- øcient conAEict resolution methods have been lacking. The recently introduced default reasoning algorithm pays special attention to conAEict resolution and in this paper the eOEciency of the conAEict resolution technique in the new algorithm is examined. To rule out classical reasoning, a fragment of default logic with only atomic formulae is considered....

110728. Learning with Extended Logic Programs - Lu'is Moniz Pereira,Evelina Lamma,Fabrizio Riguzzi
We discuss the adoption of a three-valued setting for inductive concept learning. Distinguishing between what is true, what is false and what is unknown can be useful in situations where decisions have to be taken on the basis of scarce information. In a three-valued setting, we want to learn a definition for both the target concept and its opposite, considering positive and negative examples as instances of two disjoint classes. To this purpose, we adopt extended logic programs under a well-founded semantics as the representation formalism for learning. In this way, we are able to represent both the concept and its opposite and deal with incomplete or unknown information. We discuss various approaches...

110729. A Reactive Constraint Logic Programming Scheme - F. Fages,J. Fowler
In this paper we present a constraint logic programming scheme for reactive systems. A formal framework is developed to define the scheme's operational model and to prove its completeness. A prototype implementation of a simplified version of this model is described and then evaluated on two applications. 1 Introduction The integration of constraint programming and logic programming resulted in a powerful model of computation that is conceptually simple and semantically elegant [6]. Constraint logic programming (CLP) systems have been proved successful in complex system modeling and combinatorial optimization problems. A variety of applications have been developed over the last decade across various application domains, ranging from options trading and financial...

110730. Research Report - Intelligenz Gmbh,F. M. Donini,M. Lenzerini,D. Nardi,W. Nutt,Deutsches Forschungszentrum,K Unstliche Intelligenz
The basic feature of Terminological Knowledge Representation Systems is to represent knowledge by means of taxonomies, here called terminologies, and to provide a specialized reasoning engine to do inferences on these structures. The taxonomy is built through a representation language called concept language (or description logic), which is given well-defined set-theoretic semantics. The efficiency of reasoning has often been advocated as a primary motivation for the use of such systems. Deduction methods and computational properties of reasoning problems in concept languages are the subject of this paper. The main contributions of the paper are: (1) a complexity analysis of concept satisfiability and subsumption for a wide class of concept languages;...

110731. Learning to Parse Database Queries Using Inductive Logic Programming - John M. Zelle,Raymond J. Mooney
This paper presents recent work using the Chill parser acquisition system to automate the construction of a natural-language interface for database queries. Chill treats parser acquisition as the learning of search-control rules within a logic program representing a shift-reduce parser and uses techniques from Inductive Logic Programming to learn relational control knowledge. Starting with a general framework for constructing a suitable logical form, Chill is able to train on a corpus comprising sentences paired with database queries and induce parsers that map subsequent sentences directly into executable queries. Experimental results with a complete database-query application for U.S. geography show that Chill is able to learn parsers that outperform a preexisting, hand-crafted counterpart. These results demonstrate the ability...

110732. Unknown - Chi-mei Yeung,Suet-mui Leung,Ho-fung Leung
Planning and scheduling are often NP-complete problems. There have been different approaches to tackle these problems. With the emergence of constraint logic programming, the constraint satisfaction approach has started to attract attention due to its effectness in solving these real-life problems. In this paper, we report our experience of applying constraint logic programming to fully automate the time table scheduling process in our faculty, which has been a tedious task for the administration. The system consists of a core for scheduling as well as an X-window user interface. Implemented in CHIP, the system consists of 1500 lines of codes, 80% of which are an X-window user interface. The system...

110733. Very Weak Zero One Law for Random Graphs With Order and Random Binary Functions - Saharon Shelah
Introduction In Compton Henson Shelah [CHSh245] it was proved that the zero one law fail for first order logic, for ([n]; F n ), F n the random two place function (on [n] = f1; 2; : : : ; ng) where Definition 0.1 The zero-one law for the logic L and random model M n means that for a fixed vocabulary ø , for each natural number n, ¯ n is a probablity measure on a set K n of ø - models, such that for each sentence / 2 L, the sequence hProb ¯n (M j= /) : n ! !i converge to zero...

110734. Mutable Object State for Object-Oriented Logic Programming: A Survey - Vladimir Alexiev
One of the most difficult problems on the way to an integration of Object-Oriented and Logic Programming is the modeling of changeable object state (i.e. object dynamics) in a particular logic in order not to forfeit the declarative nature of LP. Classical logic is largely unsuitable for such a task, because it adopts a general (both temporally and spatially), Platonic notion of validity, whereas object state changes over time and is local to an object. This paper presents the problem and surveys the state-of-the-art approaches to its solution, as well as some emerging, promising new approaches. The paper tries to relate the different approaches, to evaluate...

110735. Modelling Concurrency with Partial Orders - Vaughan Pratt
Concurrency has been expressed variously in terms of formal languages (typically via the shuffle operator), partial orders, and temporal logic, inter alia. In this paper we extract from these three approaches a single hybrid approach having a rich language that mixes algebra and logic and having a natural class of models of concurrent processes. The heart of the approach is a notion of partial string derived from the view of a string as a linearly ordered multiset by relaxing the linearity constraint, thereby permitting partially ordered multisets or pomsets. Just as sets of strings form languages, so do sets of pomsets form processes. We introduce a number...

110736. Implementing Integrity Control in Active Databases
This paper presents an integrity maintenance system that has been developed for maintaining static constraints in databases, using the active database paradigm. This system has been added to the O 2 object oriented database system, and is fully functional. Constraints are specified by the user in a first order logic language, and transformed in production rules, which are stored in the database. The rules are then used to maintain the corresponding set of constraints, for all applications that use the database, and which no longer need to worry about integrity control. We extend previous work on constraint maintenance in two ways: our system can be used as a constraint maintenance...

110737. PHI---A Logic-Based Tool for Intelligent Help Systems - M. Bauer,S. Biundo,D. Dengler,J. Koehler,G. Paul
We introduce a logic-based system which improves the performance of intelligent help systems by supplying them with plan generation and plan recognition components. Both components work in close mutual cooperation. There are two modes of cross-talk between them, one where plan recognition is done on the basis of abstract plans provided by the planner and the other where optimal plans are generated based on recognition results. The examples which are presented are taken from an operating system domain, namely from the unix mail domain. 1 Introduction Intelligent help systems aim at providing advanced active help to the users of complex software systems (cf. [ Breuker, 1990; Thies and Berger, 1992; Norvig et al., 1993 ] ). The...

110738. Deductive Synthesis of Numerical Simulation Programs from Networks of Algebraic and Ordinary Differential Equations - Thomas Ellman,Takahiro Murata
Scientists and engineers face recurring problems of constructing, testing and modifying numerical simulation programs. The process of coding and revising such simulators is extremely time-consuming, because they are almost always written in conventional programming languages. Scientists and engineers can therefore benefit from software that facilitates construction of programs for simulating physical systems. Our research adapts the methodology of deductive program synthesis to the problem of constructing numerical simulation codes. We have focused on simulators that can be represented as second order functional programs composed of numerical integration and root extraction routines. We have developed a system that uses first order Horn logic to synthesize numerical simulators built from...

110739. Functional Pearls: Polytypic Unification - Patrik Jansson,Johan Jeuring
Unification, or two-way pattern matching, is the process of solving an equation involving two first-order terms with variables. Unification is used in type inference in many programming languages and in the execution of logic programs. This means that unification algorithms have to be written over and over again for different term types. Many other functions also make sense for a large class of datatypes; examples are pretty printers, equality checks, maps etc. They can be defined by induction on the structure of user-defined datatypes. Implementations of these functions for different datatypes are closely related to the structure of the datatypes. We call such functions polytypic. This paper describes...

110740. Concepts and Axioms
The paper discusses the transition from informal concepts to mathematically precise notions; examples are given, and in some detail the case of lawless sequences, a concept of intuitionistic mathematics, is discussed. A final section comments on philosophical discussions concerning intuitionistic logic in connection with a "theory of meaning". What I have to tell here is not a new story, and it does not contain any really new ideas. The main difference with my earlier discussions of the same topics ([TD88, chapter16],[Tro91]) is in the emphasis. This paper starts with some examples of the transition from informal concepts to mathematically precise notions, followed by a more detailed discussion of one of these...

 

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