A timetable is a temporal arrangement of a set of meetings such that all given constraints are satisfied. A timetabling problem can be suitably modelled in terms of a set of constraints. We use constraint Logic Progra...
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Since the early days of logic programming, researchers in the field realized the potential for exploitation of parallelism present in the execution of logic programs. Their high-level nature, the presence of nondeterm...
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Since the early days of logic programming, researchers in the field realized the potential for exploitation of parallelism present in the execution of logic programs. Their high-level nature, the presence of nondeterminism, and their referential transparency, among other characteristics, make logic programs interesting candidates for obtaining speedups through parallel execution. At the same time, the fact that the typical applications of logic programming frequently involve irregular computations, make heavy use of dynamic data structures with logical variables, and involve search and speculation, makes the techniques used in the corresponding parallelizing compilers and run-time systems potentially interesting even outside the field. The objective of this article is to provide a comprehensive survey of the issues arising in parallel execution of logic programming languages along with the most relevant approaches explored to date in the field. Focus is mostly given to the challenges emerging from the parallel execution of Prolog programs, The article describes the major techniques used for shared memory implementation of Or-parallelism, And-parallelism, and combinations of the two. We also explore some related issues, such as memory management, compile-time analysis, and execution visualization.
Most cities in Germany regularly publish a booklet called the Mietspiegel. It basically contains a verbal description of an expert system. It allows the calculation of the estimated fair rent for a flat. By band, one ...
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Most cities in Germany regularly publish a booklet called the Mietspiegel. It basically contains a verbal description of an expert system. It allows the calculation of the estimated fair rent for a flat. By band, one may need a weekend to do this task. With our computerized version, the Munich Rent Advisor, the user just fills in a form in a few minutes, and the rent is calculated immediately. We also extended the functionality and applicability of the Mietspiegel so that the user need not answer all questions on the form. The key to computing with partial information using high-level programming was to use constraint logic programming. We rely on the Internet, and more specifically the World Wide Web, to provide this service to a broad user group, the citizens of Munich and the people who are planning to move to Munich. To process the answers from the questionnaire and return its result, we wrote a small simple stable special-purpose web server directly in (ECLPSe)-P-i. More than 10,000 people have used our service in the last three years. This article describes the experiences in implementing and using the Munich Rent Advisor. Our results suggest that logic programming with constraints can be an important ingredient in intelligent internet systems.
constraint programming offers modeling features and solution methods that are unavailable in mathematical programming but are often flexible and efficient for scheduling and other combinatorial problems. Yet mathemati...
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constraint programming offers modeling features and solution methods that are unavailable in mathematical programming but are often flexible and efficient for scheduling and other combinatorial problems. Yet mathematical programming is well suited to declarative modeling languages and is more efficient for some important problem classes. This raises this issue as to whether the two approaches can be combined in a declarative modeling framework. This paper proposes a general declarative modeling system in which the conditional structure of the constraints shows how to integrate any "checker" and any special-purpose "solver". In particular this integrates constraint programming and optimization methods, because the checker can consist of constraint propagation methods, and the solver can be a linear or nonlinear programming routine.
We propose PiCO, a calculus integrating concurrent objects and constraints, as a base for music composition tools. In contrast with calculi such as [5], [9] or TyCO [16], both constraints and objects are primitive not...
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We propose PiCO, a calculus integrating concurrent objects and constraints, as a base for music composition tools. In contrast with calculi such as [5], [9] or TyCO [16], both constraints and objects are primitive notions in PiCO. In PiCO a base object model is extended with constraints by orthogonally adding the notion of constraint system found in the ρ-calculus [12]. Concurrent processes make use of a constraint store to synchronize communications either via the ask and tell operations of the constraint model or the standard message-passing mechanism of the object model. A message delegation mechanism built into the calculus allows encoding of general forms of inheritance. This paper includes encodings in PiCO of the concepts of class and sub-class. These allow us to represent complex partially defined objects such as musical structures in a compact way. We illustrate the transparent interaction of constraints and objects by a musical example involving harmonic and temporal relations. The relationship between Cordial, a visual language for music composition applications, and its underlying model PiCO is described.
Approximate matching techniques based on string alignment are important tools for investigating similarities between strings, such as those representing DNA and protein sequences. We propose a constraint based approac...
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Approximate matching techniques based on string alignment are important tools for investigating similarities between strings, such as those representing DNA and protein sequences. We propose a constraint based approach for parametric sequence alignment which allows for more general string alignment queries where the alignment cost can itself be parameterized as a query with some initial constraints. Thus, the costs need not be fixed in a parametric alignment query unlike the case in normal alignment. The basic dynamic programming string edit distance algorithm is generalized to a naive algorithm which uses inequalities to represent the alignment score. The naive algorithm is rather costly and the remainder of the paper develops an improvement which prunes alternatives where it can and approximates the alternatives otherwise. This reduces the number of inequalities significantly and strengthens the constraint representation with equalities. We present some preliminary results using parametric alignment on some general alignment queries.
This paper describes our research into the expansion of the spreadsheet paradigm by the incorporation of solvers for systems of linear and finite-domain constraints. An extended spreadsheet system, called Intellisheet...
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ISBN:
(纸本)0780371984
This paper describes our research into the expansion of the spreadsheet paradigm by the incorporation of solvers for systems of linear and finite-domain constraints. An extended spreadsheet system, called Intellisheet, allows the entry of expressions that represent linear and finite-domain constraints, along with arithmetic expressions, in individual cells. The systems of constraints that have been entered are automatically solved by constraint solvers and the resulting solutions are displayed in the cells that contain the expressions or in other assigned cells. Intellisheet's GUI also has some special features to facilitate constraint programming. Incorporating constraint solvers extends the scope of the spreadsheet paradigm to declarative programming and provides an easier way to solve a broad class of problems, including linear optimization and discrete problems.
We consider the problem of specializing constraint logic programs w.r.t. constrained queries. We follow a transformational approach based on rules and strategies. The use of the rules ensures that the specialized prog...
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ISBN:
(纸本)3540421270
We consider the problem of specializing constraint logic programs w.r.t. constrained queries. We follow a transformational approach based on rules and strategies. The use of the rules ensures that the specialized program is equivalent to the initial program w.r.t. a given constrained query. The strategies guide the application of the rules so to derive an efficient specialized program. In this paper we address various issues concerning the development of an automated transformation strategy. In particular, we consider the problems of when and how we should unfold, replace constraints, introduce generalized clauses, and apply the contextual constraint replacement rule. We propose a solution to these problems by adapting to our framework various techniques developed in the field of constraint programming, partial evaluation, and abstract interpretation. In particular, we use: (i) suitable solvers for simplifying constraints, (ii) well-quasi-orders for ensuring the termination of the unfoldings and for activating clause generalizations, and (iii) widening operators for ensuring the termination of the generalization process.
Although constraint programming offers a wealth of strong, general-purpose methods, in practice a complex, real application demands a person who selects, combines, and refines various available techniques for constrai...
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Autonomous agents are a challenging concept for future unmanned air operations in hostile environments. Previous aeronautic missions highlight the lack of on-board reasoning abilities to increase the decision making c...
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ISBN:
(纸本)0780367227
Autonomous agents are a challenging concept for future unmanned air operations in hostile environments. Previous aeronautic missions highlight the lack of on-board reasoning abilities to increase the decision making capability, to efficiently react to unexpected events or to adapt plans to unexpected situation changes. If many agent-based system approaches exhibit reasoning functionalities, the complexity of air missions prevents from using the underlying generic models onto realistic missions. By taking advantage of constraint programming techniques, this paper demonstrates how a dedicated planning method can manage unmanned air vehicles into a realistic mission.
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