Static type systems in programming languages allow many errors to be detected at compile time that wouldn't be detected until runtime otherwise. Dependent types are more expressive than the type systems in most pr...
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Static type systems in programming languages allow many errors to be detected at compile time that wouldn't be detected until runtime otherwise. Dependent types are more expressive than the type systems in most programming languages, so languages that have them should allow programmers to detect more errors earlier. In this paper, using the Twelf system, we show that dependent types in the logic programming setting can be used to ensure partial correctness of programs which implement theorem provers, and thus avoid runtime errors in proof search and proof construction. We present two examples: a tactic-style interactive theorem prover and a union-find decision procedure.
Software agents are programs designed to perform tasks autonomously. Mail-agents attempt to provide useful functions about electronic mail (E-mail) service, such as information filtering, gathering, and scheduling. Wi...
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Software agents are programs designed to perform tasks autonomously. Mail-agents attempt to provide useful functions about electronic mail (E-mail) service, such as information filtering, gathering, and scheduling. With Internet use continuing to explode, the information overload is growing so fast that the same virtues that made E-mail so popular are now becoming a negative technologic boomerang (see the volume of junk or spam mail). Industria. as well as academic research has faced this problem in terms of automated filtering methods in order to distinguish, at the receiver-side, legitimate E-mail from spamming. Here we describe an alternative approach: our mail system is skilled to find, at the sender-side, "appropriate" destinations for a sending message by triggering a spidering process on (a portion of) the Web. This process performs a distributed computation using mobile agents: by applying a similarity-based reasoning on information extracted from the web pages of potential addressees, the agents are able to compute a numeric value in [0, 1] which provides, for any address, a measure of the "interest" in receiving the E-mail. The overall architecture is implemented in Java using the basic issues of Internet protocol. (C) 2003 Elsevier B.V. All rights reserved.
In this paper we describe an approach to the construction of adaptive tutoring systems, based on techniques from the research area of Reasoning about Actions and Change. This approach leads to the implementation of a ...
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In this paper we describe an approach to the construction of adaptive tutoring systems, based on techniques from the research area of Reasoning about Actions and Change. This approach leads to the implementation of a prototype system, having a multi-agent architecture, whose kernel is a set of rational agents, programmed in the logic programming language DyLOG. In the prototype that we implemented the reasoning capabilities of the agents are exploited both to dynamically build study plans and to verify the correctness of user-given study plans with respect to the competence that the user wants to acquire.
Binary logic programs can be obtained from ordinary logic programs by a binarizing transformation. In most cases, binary programs obtained this way are less efficient than the original programs. (Demoen, 1992) showed ...
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Binary logic programs can be obtained from ordinary logic programs by a binarizing transformation. In most cases, binary programs obtained this way are less efficient than the original programs. (Demoen, 1992) showed an interesting example of a logic program whose computational behaviour was improved when it, was transformed to a binary program and then specialized by partial deduction. The class of B-stratifiable logic programs is defined. It is shown that for every B-stratifiable logic program, binarization and Subsequent partial deduction produce a binary program which does not contain variables for continuations introduced by binarization. Such programs usually have a better computational behaviour than the original ones. Both binarization and partial deduction can be easily automated. A comparison with other related approaches to program transformation is given.
This paper proposes a mechanism to integrate conditional proof, which is an important proof technique in deductive logic, into logic programming to enhance the power of deduction. Concentrating on two existing resolut...
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This paper proposes a mechanism to integrate conditional proof, which is an important proof technique in deductive logic, into logic programming to enhance the power of deduction. Concentrating on two existing resolution strategies-SLD-resolution and PT-resolution, it analyses the necessity and feasibility of the integration, and formulates the procedure. (C) 2003 Elsevier Inc. All rights reserved.
This work presents the implementation of an extension of SLD resolution towards approximate reasoning and its implementation in an extended Prolog system. The proposed refutation procedure overcomes failures in the un...
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This work presents the implementation of an extension of SLD resolution towards approximate reasoning and its implementation in an extended Prolog system. The proposed refutation procedure overcomes failures in the unification process by exploiting similarity relations defined between predicate and constant symbols. This enables to compute approximate solutions, with an associated approximation degree, when failures of the exact inference process occur. In this paper we outline the main ideas of this approach and we present an extended PROLOG interpreter, named SiLog, which implements this inference procedure. Then we point out on a web-based platform, usable for knowledge discovery, that exploits as inner feature the similarity-based SLD resolution. (C) 2003 Elsevier B.V. All rights reserved.
The basic logic programming semantic concepts, query, solutions, solution forms, and the fundamental results such as Herbrand theorems, are developed over any logical system, formalised as institution, by employing &#...
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The basic logic programming semantic concepts, query, solutions, solution forms, and the fundamental results such as Herbrand theorems, are developed over any logical system, formalised as institution, by employing 'institution-independent' concepts of variable, substitution, quantifier, and atomic formulae. This sets semantical foundations for a uniform development of logic programming over a large variety of computing science logics, allowing for a clean combination of logic programming with other computing paradigms. (C) 2004 Elsevier B.V. All rights reserved.
This paper deals with the problem of modeling Web information resources using expert knowledge and personalized user information for improved Web searching capabilities. We propose a "Web information space" ...
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This paper deals with the problem of modeling Web information resources using expert knowledge and personalized user information for improved Web searching capabilities. We propose a "Web information space" model, which is composed of Web-based information resources (HTML/XML [Hypertext Markup Language/Extensible Markup Language] documents on the Web), expert advice repositories (domain-expert-specified meta-data for information resources), and personalized information about users (captured as user profiles that indicate users' preferences about experts as well as users' knowledge about topics). Expert advice, the heart of the Web information space model, is specified using topics and relationships among topics (called metalinks), along the lines of the recently proposed topic maps. Topics and metalinks constitute metadata that describe the contents of the underlying HTML/XML Web resources. The metadata specification process is semiautomated, and it exploits XML DTDs (Document Type Definition) to allow domain-expert guided mapping of DTD elements to topics and metalinks. The expert advice is stored in an object-relational database management system (DBMS). To demonstrate the practicality and usability of the proposed Web information space model, we created a prototype expert advice repository of more than one million topics/metalinks for DBLP (Database and logic programming) Bibliography data set. We also present a query interface that provides sophisticated querying facilities for DBLP Bibliography resources using the expert advice repository.
Global SLS-resolution is a well-known procedural semantics for top-down computation of queries under the well-founded model. It inherits from SLDNF-resolution the linearity property of derivations, which makes it easy...
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Global SLS-resolution is a well-known procedural semantics for top-down computation of queries under the well-founded model. It inherits from SLDNF-resolution the linearity property of derivations, which makes it easy and efficient to implement using a simple stack-based memory structure. However, like SLDNF-resolution it suffers from the problem of infinite loops and redundant computations. To resolve this problem, in this paper we develop a new procedural semantics, called SLTNF-resolution, by enhancing Global SLS-resolution with loop cutting and tabling mechanisms. SLTNF-resolution is sound and complete w.r.t. the well-founded semantics for logic programs with the bounded-term-size property, and is superior to existing linear tabling procedural semantics such as SLT resolution. (C) 2004 Elsevier B.V. All rights reserved.
A challenge of many transformation-based generators is that they are trying to achieve three mutually antagonistic goals simultaneously: 1) deeply factored operators and operands to gain the combinatorial programming ...
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A challenge of many transformation-based generators is that they are trying to achieve three mutually antagonistic goals simultaneously: 1) deeply factored operators and operands to gain the combinatorial programming leverage provided by composition, 2) high-performance code in the generated program, and 3) small (i.e., practical) generation search spaces. The Anticipatory Optimization Generator (AOG) has been built to explore architectures and strategies that address this challenge. The fundamental principle underlying all of AOG's strategies is to solve separate, narrow, and specialized generation problems by strategies that are narrowly tailored to specific problems rather than a single, universal strategy aimed at all problems. A second fundamental notion is the preservation and use of domain-specific information as a way to gain extra leverage on generation problems. This paper will focus on two specific mechanisms: 1) Localization: the generation and merging of implicit control structures and 2) Tag-Directed Transformations: a new control structure for transformation-based optimization that allows differing kinds of retained domain knowledge (e.g., optimization knowledge) to be anticipated, affixed to the component parts in the reuse library, and triggered when the time is right for its use.
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