We present a brief survey of some of the key results on the interplay between algebraic and graph-theoretic methods in the study of the complexity of digraph-based constraint satisfaction problems. 1998 ACM Subject Classification A.1 Introductory and Survey, D.3.2 Constraint and Logic Languages, F.2.2 Computations on Discrete Structures

In this paper, an airport departure scheduling tool for aircraft is presented based on constraint satisfaction techniques. Airports are getting more and more congested with the available runway configuration as one of the most constraining factors. A possibility to alleviate this congestion is to assist controllers in the planning and scheduling process of aircraft. The prototype presented here...

As a first attempt to exploit symmetries in continuous constraint problems, we focus on permutations of the variables consisting of one single cycle. We propose a procedure that takes advantage of these symmetries by interacting with a Branch-and-Prune algorithm without interfering with it. A key concept in this procedure are the classes of symmetric boxes formed by bisecting a n-dimensional cu...

The quantified constraint satisfaction problem (QCSP) is a powerful framework for modelling computational problems. The general intractability of the QCSP has motivated the pursuit of restricted cases that avoid its maximal complexity. In this paper, we introduce and study a new model for investigating QCSP complexity in which the types of constraints given by the existentially quantified varia...

I present a survey of recent advances in the algorithmic and computational complexity theory of non-Boolean Quantified Constraint Satisfaction Problems, incorporating some more modern research directions. 1998 ACM Subject Classification F.2.2 Nonnumerical Algorithms and Problems

For a digraph H, the Constraint Satisfaction Problem with template H, or CSP(H), is the problem of deciding whether a given input digraph G admits a homomorphism to H. The CSP dichotomy conjecture of Feder and Vardi states that for any digraph H, CSP(H) is either in P or NP-complete. Barto, Kozik, Maróti and Niven (Proc. Amer. Math. Soc, 2009) confirmed the conjecture for a class of oriented tr...

Combination of AI/OR methods is gaining a great deal of attention because many combinatorial problems especially in planning and scheduling areas can be solved by means of combined AI/OR techniques. Many of these combinatorial problems can be expressed in a natural way as a Constraint Satisfaction Problem (CSP). It is well known that a non-binary CSP can be transformed into an equivalent binary...

An algorithm called QUICKTREE is developed for finding a triangulation T of a given undirected graph G such that the size of T’s maximal clique is minimum and such that no other triangulation of G is a subgraph of T. We have tested QUICKTREE on graphs of up to 100 nodes for which the maximum clique in an optimal triangulation is of size 11. This is the first algorithm that can optimally triangu...

job satisfaction of nurses working in hospitals in zahedan purgaz a , nastiezaie n , hezare mogadam m received: 15 april, 2010 accepted: 27july, 2010 abstract background & aims: one of the most important elements of any organization especially health organizations is human resources. job satisfaction leads to being interested or disinterested. the present study aimed to determine the job satisf...

Workflow verification is an important aspect of workflow modeling where the verification task is to ensure that the workflow describes feasible processes. It has been shown that verifying nested workflows with extra precedence, causal, and temporal synchronization constraints is an NPcomplete problem and a verification method based on constraint satisfaction has been proposed. This paper theore...