This paper is focused on a double extension of traditional logic programming which enhances it following two different approaches. On one hand, extending Horn logic to hereditary Harrop formulas (HH), in order to impr...
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ISBN:
(纸本)1581138199
This paper is focused on a double extension of traditional logic programming which enhances it following two different approaches. On one hand, extending Horn logic to hereditary Harrop formulas (HH), in order to improve the expressive power;on the other, incorporating constraints, in order to increase the efficiency. For this combination, called HH(C), an operational semantics exists, but no declarative semantic for it has been defined so far. One of the main features of (Constraint) logic programming is that the algorithmic behavior of (constraint) logic programs and its mathematical interpretations agree with each other, in the sense that the declarative meaning of a program can be interpreted operationally as a goal-oriented search for solutions. Both operational (algorithmic) and declarative (mathematical) semantics for programs are useful and widely developed in the frame of logic programming as well as in its extension, Constraint logic programming. For these reasons, HH(C) was in need of a more mathematical interpretation of programs. In this paper some fixed point semantics for HH(C) are presented. Taking as a starting point the techniques used by Miller to interpret the fragment of HH that incorporates intuitionistic implication in goals, we have formulated two novel extensions capable of dealing with the whole HH logic, including universal quantifiers, as well as with the presence of constraints. Those semantics are proved to be sound and complete w.r.t. the operational semantics of HH(C).
Compatible Observability Don't Cares (CODCs) are a powerful means to express the flexibility present at a node in a multi-level logic network. Despite their elegance, the applicability of CODCs has been hampered b...
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ISBN:
(纸本)1511838288
Compatible Observability Don't Cares (CODCs) are a powerful means to express the flexibility present at a node in a multi-level logic network. Despite their elegance, the applicability of CODCs has been hampered by their computational complexity. The CODC computation for a network involves several image computations, which require the construction of global BDDs of the circuit nodes. The size of BDDs of circuit nodes is unpredictable, and as a result, the CODC computation is not robust. In practice, CODCs cannot be computed for large circuits due to this limitation. In this paper, we present an algorithm to compute approximate CODCs (ACODCs). This algorithm allows us to compute compatible don't cares for significantly larger designs. Our ACODC algorithm is scalable in the sense that the user may trade off time and memory against the accuracy of the ACODCs computed. The ACODC is computed by considering a subnetwork rooted at the node of interest, up to a certain topological depth, and performing its don't care computation. We prove that the ACODC is an approximation of its CODC. We have proved the soundness of the approach, and performed extensive experiments to explore the trade-off between memory utilization, speed and accuracy. We show that even for small topological depths, the ACODC computation gives very good results. Our experiments demonstrate that our algorithm can compute ACODCs for circuits whose CODC computation has not been demonstrated to date. Also, for a set of benchmark circuits whose CODC computation yields an average 28% reduction in literals after optimization, our ACODC computation yields an average 22% literal reduction. Our algorithm has runtimes which are about 25× and memory utilization which is 33× better that of the CODC computation of SIS.
Tracing computations is a widely used methodology for program debugging. Lazy languages, in particular, pose new demands on tracing techniques since following the actual trace of a computation is generally useless. Ty...
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ISBN:
(纸本)9781581138351
Tracing computations is a widely used methodology for program debugging. Lazy languages, in particular, pose new demands on tracing techniques since following the actual trace of a computation is generally useless. Typically, they rely on the construction of a redex trail, a graph that describes the reductions of a computation and its relationships. While tracing provides a significant help for locating bugs, the task still remains complex. A well-known debugging technique for imperative programs is based on dynamic slicing, a method to find the program statements that influence the computation of a value for a specific program input. In this work, we introduce a novel technique for dynamic slicing in lazy functional logic languages. Rather than starting from scratch, our technique relies on (a slight extension of) redex trails. We provide a method to compute a correct and minimal dynamic slice from the redex trail of a computation. A clear advantage of our proposal is that one can enhance existing tracers with slicing capabilities with a modest implementation effort, since the same data structure (the redex trail) can be used for both tracing and slicing.
This paper presents a framework that integrates three aspects of agency: planning, for proactive behaviour, negotiation, for social behaviour and resource achievement, and control of operation, for reconciling rationa...
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ISBN:
(纸本)9781586034528
This paper presents a framework that integrates three aspects of agency: planning, for proactive behaviour, negotiation, for social behaviour and resource achievement, and control of operation, for reconciling rationality with reactivity. Agents are designed and programmed in a computational logic-based language where these aspects are accommodated in a declarative and modular way. We show how this framework can be applied to agent problems requiring negotiation and resource achievement and present some of its formal properties. The framework can be implemented based on a communication platform for agent interaction and on well-established logic programming technologies for agent reasoning.
We explore the use of a number of logic programming techniques for generating dynamic Web content and the underlying architecture and implementation issues. We describe a Prolog to VRML mapping allowing generation of ...
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We present a generalisation of first-order rewriting which allows us to deal with terms involving binding operations in an elegant and practical way. We use a nominal approach to binding, in which bound entities are e...
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ISBN:
(纸本)1581138199
We present a generalisation of first-order rewriting which allows us to deal with terms involving binding operations in an elegant and practical way. We use a nominal approach to binding, in which bound entities are explicitly named (rather than using a nameless syntax such as de Bruijn indices), yet we get a rewriting formalism which respects α-conversion and can be directly implemented. This is achieved by adapting to the rewriting framework the powerful techniques developed by Pitts et al. in the FreshML project. Nominal rewriting can be seen as higher-order rewriting with a first-order syntax and built-in α-conversion. We show that standard (first-order) rewriting is a particular case of nominal rewriting, and that very expressive higher-order systems such as Klop's Combinatory Reduction Systems can be easily defined as nominal rewriting systems. Finally we study confluence properties of nominal rewriting.
In this article we sustain that Contextual Constraint logic programming (CxCLP for short) is a useful paradigm in which to specify and implement Organizational Information Systems, particularly when integrated with th...
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ISBN:
(纸本)9728865007
In this article we sustain that Contextual Constraint logic programming (CxCLP for short) is a useful paradigm in which to specify and implement Organizational Information Systems, particularly when integrated with the ISCO mediator framework. We briefly introduce the language and its underlying paradigm, appraising it from the angle of both of its ancestries: logic and Object-Oriented programming. An initial implementation has been developed and is being actively used in a real-world setting - Universidade de vora's Academic Information System. We briefly describe both the prototype implementation and its first large-scale application. We conclude that the risk taken in adopting a developing technology such as the one presented herein for a mission-critical system has paid off, in terms of both development ease and flexibility as well as in maintenance requirements.
The data on which a MLP (multi-layer perception) is to be trained to approximate a continuous function may include inputs that are categorical rather than only numeric or quantitative. However an MLP with connection m...
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ISBN:
(纸本)0889864586
The data on which a MLP (multi-layer perception) is to be trained to approximate a continuous function may include inputs that are categorical rather than only numeric or quantitative. However an MLP with connection matrices that multiply input values and sigmoid functions that further transform values represents a continuous mapping in all input variables. A MLP therefore requires that all inputs correspond to numeric, continuously valued variables and represents a continuous function in all input variables. On the other hand a categorical variable produces a discontinuous relationship between an input variable and the output. The way that this problem is often dealt with is to replace the categorical values by numeric ones and treat them as if they were continuously valued. However there is no meaningful correspondence between the continuous quantities generated this way and the original categorical values. An approach examined in this paper is to train a standard feedforward network with the numeric portion of the input only and train another network with the categorical portion of the input to produce a selector vector. The selector vector produced by the second network selects output from the first network.
Linear temporal logic (LTL) has been widely used for specification and verification of reactive systems. Its standard model is sequences of states (or state transitions), and formulas describe sequencing of state tran...
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The following problem will be considered: from scattered examples on the behavior of a dynamic system induce a description of the system. For the induced description to be concise and modular, we use a generic action ...
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