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SemiringBased Constraint Satisfaction and Optimization
 JOURNAL OF THE ACM
, 1997
"... We introduce a general framework for constraint satisfaction and optimization where classical CSPs, fuzzy CSPs, weighted CSPs, partial constraint satisfaction, and others can be easily cast. The framework is based on a semiring structure, where the set of the semiring specifies the values to be asso ..."
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Cited by 207 (26 self)
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We introduce a general framework for constraint satisfaction and optimization where classical CSPs, fuzzy CSPs, weighted CSPs, partial constraint satisfaction, and others can be easily cast. The framework is based on a semiring structure, where the set of the semiring specifies the values to be associated with each tuple of values of the variable domain, and the two semiring operations (1 and 3) model constraint projection and combination respectively. Local consistency algorithms, as usually used for classical CSPs, can be exploited in this general framework as well, provided that certain conditions on the semiring operations are satisfied. We then show how this framework can be used to model both old and new constraint solving and optimization schemes, thus allowing one to both formally justify many informally taken choices in existing schemes, and to prove that local consistency techniques can be used also in newly defined schemes.
Directed Hypergraphs And Applications
, 1992
"... We deal with directed hypergraphs as a tool to model and solve some classes of problems arising in Operations Research and in Computer Science. Concepts such as connectivity, paths and cuts are defined. An extension of the main duality results to a special class of hypergraphs is presented. Algorith ..."
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Cited by 141 (5 self)
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We deal with directed hypergraphs as a tool to model and solve some classes of problems arising in Operations Research and in Computer Science. Concepts such as connectivity, paths and cuts are defined. An extension of the main duality results to a special class of hypergraphs is presented. Algorithms to perform visits of hypergraphs and to find optimal paths are studied in detail. Some applications arising in propositional logic, AndOr graphs, relational data bases and transportation analysis are presented. January 1990 Revised, October 1992 ( * ) This research has been supported in part by the "Comitato Nazionale Scienza e Tecnologia dell'Informazione", National Research Council of Italy, under Grant n.89.00208.12, and in part by research grants from the National Research Council of Canada. 1 Dipartimento di Informatica, Università di Pisa, Italy 2 Département d'Informatique et de Recherche Opérationnelle, Université de Montréal, Canada 2 INTRODUCTION Hypergraphs, a generaliz...
Directed Hypergraphs as a Modelling Paradigm
 RIVISTA AMASES
, 1999
"... We address a generalization of graphs, the directed hypergraphs, and show that they are a powerful tool in modelling and solving several relevant problems in many application areas. Such application areas include Linear Production Problems, Flexible Manufacturing Systems, Propositional Logic, Relat ..."
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Cited by 14 (1 self)
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We address a generalization of graphs, the directed hypergraphs, and show that they are a powerful tool in modelling and solving several relevant problems in many application areas. Such application areas include Linear Production Problems, Flexible Manufacturing Systems, Propositional Logic, Relational Databases, and Public Transportation Systems.
Structure and Design of Problem Reduction Generators
 Client Resources on the Internet, IEEE Multimedia Systems ’99
, 1991
"... In this paper we present an axiomatic theory for a class of algorithms, called problem reduction generators, that includes dynamic programming, general branchandbound, and game tree search as special cases. This problem reduction theory is used as the basis for a mechanizable design tactic that tr ..."
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Cited by 13 (6 self)
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In this paper we present an axiomatic theory for a class of algorithms, called problem reduction generators, that includes dynamic programming, general branchandbound, and game tree search as special cases. This problem reduction theory is used as the basis for a mechanizable design tactic that transforms formal specifications into problem reduction generators. The theory and tactic are illustrated by application to the problem of enumerating optimal binary search trees. Contents 1. Introduction 3 2. Basic Concepts And Notation 3 2.1. Language . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Signatures and Structures . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.3. Problem Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Enumerating Feasible Solutions 6 3.1. Problem Reduction Theory . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2. Design Tactic  Enumerating Feasible Solutions . . . . . . . . . . . . . ....
Parallel BestFirst BranchandBound in Discrete Optimization: a Framework
 IN SOLVING COMBINATORIAL OPTIMIZATION PROBLEMS IN PARALLEL
, 1995
"... In discrete optimization problems, we search for an optimal solution among all vectors in a discrete solution space that satisfy a set of constraints, and the search efficiency is of considerable importance since exhaustive search is often impracticable. The method called branchandbound (noted B&a ..."
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Cited by 8 (1 self)
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In discrete optimization problems, we search for an optimal solution among all vectors in a discrete solution space that satisfy a set of constraints, and the search efficiency is of considerable importance since exhaustive search is often impracticable. The method called branchandbound (noted B&B) is a heuristic tree search algorithm used in this context. Its principle lies in successive decompositions of the original problem in smaller disjoint subproblems until an optimal solution is found, and the search avoids visiting some subproblems which are known not to contain an optimal solution. Given that disjoint subproblems can be decomposed simultaneously and independently, parallel processing has been widely considered as an additional source of improvement in search efficiency, using the set of processors to concurrently decompose several subproblems at each iteration. Parallel B&B is traditionally considered as an irregular parallel algorithm due to the fact that the structure o...
Higher Order Semiringbased Constraints
"... Abstract Semiringbased constraint problems (SCSPs) [BMR95,BMR97] extend classical constraint problems (CSPs) by allowing preferences, costs, priorities, probabilities, and other soft features. They are based over the notion of a semiring, that is, a set plus two operations. In this paper we introdu ..."
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Abstract Semiringbased constraint problems (SCSPs) [BMR95,BMR97] extend classical constraint problems (CSPs) by allowing preferences, costs, priorities, probabilities, and other soft features. They are based over the notion of a semiring, that is, a set plus two operations. In this paper we introduce a uniform, abstract presentation of (soft) constraint satisfaction concepts and constructions. Moreover, the soft constraint environment is enriched with the operation of function abstraction and application that can suitably be used to give modularity and compositionality to the framework. Finally, a small language is defined and used to represent and give semantics to general local propagation and dynamic programming algorithms. 1
IOS Press Guesteditorial: A Journey in Computational Logic in Italy
"... This issue reviews the recent work of the Italian research groups, whose activity focuses on the use of methodologies and of techniques that are based on computational logic, a fundamental research area of Artificial Intelligence. The study of computational logic has a long tradition in Italy. GULP ..."
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This issue reviews the recent work of the Italian research groups, whose activity focuses on the use of methodologies and of techniques that are based on computational logic, a fundamental research area of Artificial Intelligence. The study of computational logic has a long tradition in Italy. GULP (the name of the Italian Association for Logic Programming), with its 25 years of existence, is the oldest national association ever founded on this topic, even older than the international Association for Logic Programming. It was, in fact, founded in 1985, soon raising to the highest international levels and becoming the promoter of initiatives that provided both educational and scientific opportunities to many young researchers. After 2004, researchers realized that the time was mature for opening to neighboring and applicative fields and to start proposing logic programming also as a tool for solving problems of interest to other disciplines. The aim of this special issue is to witness this effort. As such, it complements the survey of the first twentyfive years of existence of GULP, edited by Agostino Dovier and Enrico Pontelli in 2010. The fifteen selected articles, included in the special issue, describe some of the most relevant recent experiences and some of the most promising investigations that were (and are being) carried on in such diverse fields as the (Semantic) Web, the specification and verification of interaction protocols, bioinformatics, intelligent agents, nonmonotonic reasoning, business processes, program transformation, nonclassical logics and knowledge representation, and constraint programming. On the whole, fortyeight researchers * Corresponding author.