This paper presents the multi-threading and internet message communication capabilities of Qu-Prolog. Message addresses are symbolic and the communications package provides high-level support that completely hides det...
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This paper presents the multi-threading and internet message communication capabilities of Qu-Prolog. Message addresses are symbolic and the communications package provides high-level support that completely hides details of IP addresses and port numbers as well as the underlying TCP/IP transport layer. The combination of the multi-threads and the high level inter-thread message communications provide simple, powerful support for implementing internet distributed intelligent applications.
作者：
Maher, MJLoyola Univ
Dept Math & Comp Sci Chicago IL 60611 USA Griffith Univ
Sch Comp & Informat Technol Nathan Qld 4111 Australia
Defeasible logic is a rule-based nonmonotonic logic, with both strict and defeasible rules, and a priority relation on rules. We show that inference in the propositional form of the logic can be performed in linear ti...
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Defeasible logic is a rule-based nonmonotonic logic, with both strict and defeasible rules, and a priority relation on rules. We show that inference in the propositional form of the logic can be performed in linear time. This contrasts markedly with most other propositional nonmonotonic logics, in which inference is intractable.
We introduce A(k), an extension of the action description language A (Gelfond and Lifschitz, 1993) to handle actions which affect knowledge. We use sensing actions to increase an agent's knowledge of the world and...
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We introduce A(k), an extension of the action description language A (Gelfond and Lifschitz, 1993) to handle actions which affect knowledge. We use sensing actions to increase an agent's knowledge of the world and non-deterministic actions to remove knowledge. We include complex plans involving conditionals and loops in our query language for hypothetical reasoning. We also present a translation of A(k) domain descriptions into epistemic logic programs.
We study here a natural situation when constraint programming can be entirely reduced to rule-based programming. To this end we explain first how one can compute on constraint satisfaction problems using rules represe...
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We study here a natural situation when constraint programming can be entirely reduced to rule-based programming. To this end we explain first how one can compute on constraint satisfaction problems using rules represented by simple first-order formulas. Then we consider constraint satisfaction problems that are based on predefined. explicitly given constraints. To solve them we first derive rules from these explicitly given constraints and limit the computation process to a repeated application of these rules, combined with labeling. We consider two types of rule here, The first type, that we call equality rules, leads to a new notion of local consistency, called rule consistency that turns out to be weaker than arc consistency for constraints of arbitrary arity (called hyper-arc consistency in Marriott & Stuckey (1998)). For Boolean constraints rule consistency coincides with the closure under the well-known propagation rules for Boolean constraints, The second type of rules, that we call membership rules, yields a rule-based characterization of arc consistency. To show feasibility of this rule-based approach to constraint programming. we show how both types of rules can be automatically generated. as CHR rules of Fruhwirth (1995). This yields an implementation of this approach to programming by means of constraint logicprogramming. We illustrate the usefulness of this approach to constraint programming by discussing various examples, including Boolean constraints, two typical examples of many valued logics, constraints dealing with Waltz's language for describing polyhedral scenes, and Allen's qualitative approach to temporal logic.
We discuss from a practical point of view a number of issues involved in writing distributed Internet and WWW applications using LP/CLP systems. We describe PiLLoW, a public-domain Internet and WWW programming library...
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We discuss from a practical point of view a number of issues involved in writing distributed Internet and WWW applications using LP/CLP systems. We describe PiLLoW, a public-domain Internet and WWW programming library for LP/CLP systems that we have designed to simplify the process of writing such applications. PiLLoW provides facilities for accessing documents and code on the WWW;parsing, manipulating and generating HTML and XML structured documents and data;producing HTML forms;writing form handlers and CGI-scripts;and processing HTML/XML templates. An important contribution of PiLLoW is to model HTML/XML code (and, thus, the content of WWW pages) as terms. The PiLLoW library has been developed in the context of the Ciao Prolog system, but it has been adapted to a number of popular LP/CLP systems, supporting most of its functionality. We also describe the use of concurrency and a high-level model of client-server interaction, Ciao Prolog's active modules, in the context of WWW programming. We propose a solution for client-side downloading and execution of Prolog code, using generic browsers. Finally, we also provide an overview of related work on the topic.
We present verification methods for logic programs with delay declarations. The verified properties are termination and freedom from errors related to built-ins. Concerning termination, we present two approaches. The ...
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We present verification methods for logic programs with delay declarations. The verified properties are termination and freedom from errors related to built-ins. Concerning termination, we present two approaches. The first approach tries to eliminate the well-known problem of speculative output bindings. The second approach is based on identifying the predicates for which the textual position of an atom using this predicate is irrelevant with respect to termination. Three features are distinctive of this work: it allows for predicates to be used in several modes;it shows that block declarations, which are a very simple delay construct, are sufficient to ensure the desired properties;it takes the selection rule into account, assuming it to be as in most Prolog implementations. The methods can be used to verify existing programs and assist in writing new programs.
Infinite loops and redundant computations are long recognized open problems in Prolog. Two methods have been explored to resolve these problems: loop checking and tabling. Loop checking can cut infinite loops, but it ...
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Infinite loops and redundant computations are long recognized open problems in Prolog. Two methods have been explored to resolve these problems: loop checking and tabling. Loop checking can cut infinite loops, but it cannot be both sound and complete even for function-free logic programs. Tabling seems to be an effective way to resolve infinite loops and redundant computations. However, existing tabulated resolutions, such as OLDT-resolution, SLG-resolution and Tabulated SLS-resolution, are non-linear because they rely on the solution-lookup mode in formulating tabling, The principal disadvantage of non-linear resolutions is that they cannot be implemented using a simple stack-based memory structure like that in Prolog. Moreover, some strictly sequential operators such as cuts may not be handled as easily as in Prolog. In this paper, we propose a hybrid method to resolve infinite loops and redundant computations. We combine the ideas of loop checking and tabling to establish a linear tabulated resolution called TP-resolution. TP-resolution has two distinctive features: (1) it makes linear tabulated derivations in the same way as Prolog except that infinite loops are broken and redundant computations are reduced. It handles cuts as effectively as Prolog;and (2) it is sound and complete for positive logic programs with the bounded-term-size property. The underlying algorithm can be implemented by an extension to any existing Prolog abstract machines such as WAM or ATOAM.
As an invited contributor to this Festschrift honoring Alain Colmerauer, I feel compelled to give not only an account of his main research contributions, but also of my perspective on the motivations behind them. I ho...
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As an invited contributor to this Festschrift honoring Alain Colmerauer, I feel compelled to give not only an account of his main research contributions, but also of my perspective on the motivations behind them. I hope that this will provide the reader with a glimpse of how a focused, tenacious, rigorous, and inventive mind like Alain's picks research problems and proceeds to solve them. The history of Prolog, the language that remains one of Alain's major accomplishments, is well documented. His paper on the ‘BirthofProlog,’ co-authored with Philippe Roussel (Colmerauer & Roussel, 1970), is a highly recommended account of the circumstances that led to the development of Prolog. Bob Kowalski (1988) presents his views of the early history of Prolog from the automatic theorem proving perspective. Finally, my own paper on the topic (Cohen, 1988) contains material complementing Alain's and Bob's narratives. Instead of recasting already-available historical material, I have opted to present here a more personal account of Alain's contributions, acknowledging in advance the individual bias inherent in such an accounting of long-past events.
In organizations where duty is around the clock, seven days a week and every week of the year, timetabling is a very difficult task, juggling between the workload and the constraints to be respected. Our work concerns...
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ISBN:
(纸本)3540424210
In organizations where duty is around the clock, seven days a week and every week of the year, timetabling is a very difficult task, juggling between the workload and the constraints to be respected. Our work concerns cyclical timetabling. This is not just duplicating a fixed sequence of assignments, but has to consider fixed annual leave, and various regulations on assignments on successive days. In some cases, the cycle sequence has to be relaxed and cycle length shortened or extended. In other cases, a small change in leave dates is allowed, except in summer. This paper describes the context and the use of work cycles in the real world, proposes an abstract model to take into account the various constraints, and finally shows how to implement an effective solution using constraint logicprogramming (in particular, CHIP V5) to produce timetables of up to 150 people over a yearly horizon.
Although several access control policies can be devised for controlling access to information, all existing authorization models, and the corresponding enforcement mechanisms, are based on a specific policy (usually t...
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Although several access control policies can be devised for controlling access to information, all existing authorization models, and the corresponding enforcement mechanisms, are based on a specific policy (usually the closed policy). As a consequence, although different policy choices are possible in theory, in practice only a specific policy can actually be applied within a given system. In this paper, we present a unified framework that can enforce multiple access control policies within
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