Results 1  10
of
31
A new approach to modeling and solving minimal perturbation problems
 In Recent Advances in Constraints
, 2004
"... Abstract. Formulation of many reallife problems evolves when the problem is being solved. For example, a change in the environment might appear after the initial problem specification and this change must be reflected in the solution. Such changes complicate usage of a traditionally static constrai ..."
Abstract

Cited by 20 (4 self)
 Add to MetaCart
(Show Context)
Abstract. Formulation of many reallife problems evolves when the problem is being solved. For example, a change in the environment might appear after the initial problem specification and this change must be reflected in the solution. Such changes complicate usage of a traditionally static constraint satisfaction technology that requires the problem to be fully specified before the solving process starts. In this paper, we propose a new formal description of changes in the problem formulation called a minimal perturbation problem. This description focuses on the modification of the solution after a change in the problem specification. We also describe a new branchandbound like algorithm for solving such type of problems.
Interactivity in Constraint programming
 IN OZ. DFKI OZ DOCUMENTATION SERIES, GERMAN RESEARCH CENTER FOR ARTIFICIAL INTELLIGENCE (DFKI), STUHLSATZENHAUSWEG 3, D66123 SAARBR UCKEN
, 1994
"... In the current computing environment, the interactive behaviour of software is a significant feature requested by many users. The minimal perturbation problem is often highly demanded and, in a sense, it seems to be very close to the interactivity. In this paper we want to compare these two features ..."
Abstract

Cited by 15 (6 self)
 Add to MetaCart
In the current computing environment, the interactive behaviour of software is a significant feature requested by many users. The minimal perturbation problem is often highly demanded and, in a sense, it seems to be very close to the interactivity. In this paper we want to compare these two features and also summarize their main demands and impacts on the constraint satisfaction problem. We also suggest several improvements toward these features.
Modeling and solution of a complex university course timetabling problem
 Practice And Theory of Automated Timetabling, Selected Revised Papers
, 2007
"... Abstract. The modeling and solution approaches being used to automate construction of course timetables at a large university are discussed. A course structure model is presented that allows this complex realworld problem to be described using a classical formulation. The problem is then tackled ut ..."
Abstract

Cited by 14 (8 self)
 Add to MetaCart
(Show Context)
Abstract. The modeling and solution approaches being used to automate construction of course timetables at a large university are discussed. A course structure model is presented that allows this complex realworld problem to be described using a classical formulation. The problem is then tackled utilizing a course timetabling solver model that transforms it into a constraint satisfaction and optimization problem. The tiered structure of this approach provides flexibility that is helpful in solving the multiple subproblems that arise from decomposition of the universitywide problem. A production system has been partially implemented and results of early use are presented. Practical issues raised during the implementation of the automated timetabling system are also discussed. 1
Minimal Perturbation Problem in Course Timetabling
"... Many reallife problems are dynamic, with changes in the problem definition occurring after a solution to the initial formulation has been reached. The minimal perturbation problem incorporates these changes, along with the initial solution, as a new problem whose solution must be as close as po ..."
Abstract

Cited by 12 (4 self)
 Add to MetaCart
Many reallife problems are dynamic, with changes in the problem definition occurring after a solution to the initial formulation has been reached. The minimal perturbation problem incorporates these changes, along with the initial solution, as a new problem whose solution must be as close as possible to the solution of an initial problem.
Soft CLP(FD
 Proceedings of the 16th International Florida Artificial Intelligence Symposium, FLAIRS03
, 2003
"... Abstract Overconstrained problems can be solved with the help of soft constraints. Weighted constraints are a typical representation of soft constraints used to minimize weights of unsatisfied constraints. A natural extension of the CLP(FD) approach is presented which allows handling of weighted s ..."
Abstract

Cited by 6 (4 self)
 Add to MetaCart
Abstract Overconstrained problems can be solved with the help of soft constraints. Weighted constraints are a typical representation of soft constraints used to minimize weights of unsatisfied constraints. A natural extension of the CLP(FD) approach is presented which allows handling of weighted soft constraints. To achieve this goal, the costs associated with unsatisfied constraints is accumulated for each problem variable and its value. For the approach proposed, implementation of the soft constraint solver on top of the existing CLP(FD) library of SICStus Prolog is described. A large scale timetabling implementation demonstrates practical application of the approach presented.
INCOMPLETE DEPTHFIRST SEARCH TECHNIQUES: A SHORT Survey
 CPDC’2004
, 2004
"... Constraint Satisfaction Problem (CSP) is a discrete combinatorial problem and hence search algorithms belong to the main constraint satisfaction techniques. There exist local search techniques exploring complete but inconsistent assignments and depthfirst search techniques extending partial consis ..."
Abstract

Cited by 6 (0 self)
 Add to MetaCart
Constraint Satisfaction Problem (CSP) is a discrete combinatorial problem and hence search algorithms belong to the main constraint satisfaction techniques. There exist local search techniques exploring complete but inconsistent assignments and depthfirst search techniques extending partial consistent assignments towards complete assignments. For most problems it is impossible to explore complete search space so incomplete techniques are used. In this paper, we survey incomplete depthfirst search techniques, in particular, generic incomplete search techniques and discrepancybased search techniques.
A supernodal formulation of vertex colouring with applications in course timetabling
, 2009
"... For many problems in Scheduling and Timetabling the choice of an mathematical programming formulation is determined by the formulation of the graph colouring component. This paper briefly surveys seven known integer programming formulations of vertex colouring and introduces a new formulation using ..."
Abstract

Cited by 6 (2 self)
 Add to MetaCart
(Show Context)
For many problems in Scheduling and Timetabling the choice of an mathematical programming formulation is determined by the formulation of the graph colouring component. This paper briefly surveys seven known integer programming formulations of vertex colouring and introduces a new formulation using “supernodes”. In the definition of George and McIntyre [SIAM J. Numer. Anal. 15 (1978), no. 1, 90–112], “supernode” is a complete subgraph, where each two vertices have the same neighbourhood outside of the subgraph. Seen another way, the algorithm for obtaining the best possible partition of an arbitrary graph into supernodes, which we give and show to be polynomialtime, makes it possible to use any formulation of vertex multicolouring to encode vertex colouring. The power of this approach is shown on the benchmark problem of Udine Course Timetabling. Results from empirical tests on DIMACS colouring instances, in addition to instances from other timetabling applications, are also provided and discussed.
A new algorithm for maintaining arc consistency after constraint retraction
 In Principles and Practice of Constraint Programming
, 2004
"... Abstract. Dynamic Constraint Satisfaction Problems play a very important role in modeling and solving reallife problems where the set of constraints is changing. The paper addresses a problem of maintaining arc consistency after removing a constraint from the constraint model. A new dynamic arc con ..."
Abstract

Cited by 4 (1 self)
 Add to MetaCart
(Show Context)
Abstract. Dynamic Constraint Satisfaction Problems play a very important role in modeling and solving reallife problems where the set of constraints is changing. The paper addresses a problem of maintaining arc consistency after removing a constraint from the constraint model. A new dynamic arc consistency algorithm is proposed that improves the practical time efficiency of the existing ACDC algorithm by using additional datastructures. The algorithm achieves real time efficiency close to the so far fastest DynAC6 algorithm while keeping the memory consumption low. 1
Limited Assignments: A New Cutoff Strategy for Incomplete DepthFirst Search
 IN PROCEEDINGS OF THE 2005 ACM SYMPOSIUM ON APPLIED COMPUTING. ACM
, 2005
"... In this paper, we propose an extension of three incomplete depthfirst search techniques, namely depthbounded backtrack search, credit search, and iterative broadening, towards producing incomplete solutions. We also propose a new cutoff strategy for incomplete depthfirst search motivated by a huma ..."
Abstract

Cited by 4 (1 self)
 Add to MetaCart
(Show Context)
In this paper, we propose an extension of three incomplete depthfirst search techniques, namely depthbounded backtrack search, credit search, and iterative broadening, towards producing incomplete solutions. We also propose a new cutoff strategy for incomplete depthfirst search motivated by a human style of problem solving. This technique, called limited assignment number (LAN) search, is based on limiting the number of attempts tried to assign a value to the variable. A linear worstcase time complexity of LAN Search leads to promising stable time behavior in all accomplished experiments. The techniques are studied in the context of constraint satisfaction problems.