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# Topic: Constraint

###### In the News (Fri 24 May 13)

 Constraint - Wikipedia, the free encyclopedia In mathematics, a constraint is a restriction of the feasible solutions in an optimization problem. In the theory of constraints, it is any factor that limits the performance of a system with respect to its goal. The concept of constraint is the basis for Goldratt's process of focused improvement. en.wikipedia.org /wiki/Constraint   (275 words)

 Constraint programming - Wikipedia, the free encyclopedia Constraints differ from the common primitives of other programming languages in that they do not specify a set of steps for finding a solution but rather the properties such solution is expected to satisfy. Constraints are embedded in an imperative language in Kaleidoscope. Constraint propagation may solve the problem by reducing all domains to a single value, it may prove that the problem has no solution by reducing a domain to the empty set, but may also terminate without proving satisfiability or unsatisfiability. en.wikipedia.org /wiki/Constraint_programming   (810 words)

 UW Constraint-Based Systems   (Site not responding. Last check: 2007-10-07) A constraint is a relation that should be satisfied -- for example, that a line remain horizontal, that a resistor in an electrical circuit simulation obey Ohm's Law, or that one column in a web page table be at least twice as wide as another. Constraints have been used in a variety of languages and systems, particularly in user interface toolkits, in planning and scheduling, and in simulation. UW constraints research has been in several areas, including the design and implementation of constraint solvers, applying constraints to user interface construction and to simulation, and the design and implementation of constraint programming languages. www.cs.washington.edu /research/constraints   (304 words)

 Introduction to Constraints Constraints are effectively global requirements, such as limited development resources or a decision by senior management that restricts the way you develop a system. Constraints can be economic, political, technical, or environmental and pertain to your project resources, schedule, target environment, or to the system itself. Constraints can be a little confusing because of their overlap with business rules and technical requirements. www.agilemodeling.com /artifacts/constraint.htm   (947 words)

 CONSTRAINT   (Site not responding. Last check: 2007-10-07) Constraints are limitations imposed by nature or by man that do not permit certain actions to be taken. The actions, alternatives, consequences, and objectives that are not precluded by the constraints are referred to as [feasible.] In a particular analysis study, some constraints may have to be considered [stiff] or unquestionable, others--from among those imposed by prior decisions--may be [elastic] or removable if the analysis proves a good case for it. For an observer, constraints become apparent when he finds that a system can assume fewer states than are logically possible or hypothesized by him. pespmc1.vub.ac.be /ASC/CONSTRAINT.html   (325 words)

 TDAN - Hay - Business Constraint Metamodel The constraint we are after is called a “join-subset constraint”, and in Figure 5 this is represented by the lines linking the relationship from test to test type to a line between the test type / test requirement relationship and the test / sample relationship. A business constraint must be either an integrity business constraint or a condition, and it may be to constrain an entity class, a role, or an attribute. The business constraint may be composed of one or more business constraint elements, each of which refers to something doing the constraining—an attribute, a role, an entity class, or another business constraint. www.tdan.com /i029ht02.htm   (1654 words)

 Constraint Guide - Introduction   (Site not responding. Last check: 2007-10-07) Constraint programming is an emergent software technology for declarative description and effective solving of large, particularly combinatorial, problems especially in areas of planning and scheduling. A constraint is simply a logical relation among several unknowns (or variables), each taking a value in a given domain. The idea of constraint programming is to solve problems by stating constraints (conditions, properties) which must be satisfied by the solution. kti.ms.mff.cuni.cz /~bartak/constraints/intro.html   (890 words)

 Constraint-Based Reasoning Constraint propagation, which is Choueiry’s speciality, is just one method of reasoning for artificial intelligence. "Constraints provides a common forum for the many disciplines interested in constraint programming and constraint satisfaction and optimization, and the many application domains in which constraint technology is employed. Constraint- based reasoning systems can be enhanced by using agents with multiple problem-solving approaches or diverse problem representations. www.aaai.org /AITopics/html/conbase.html   (1128 words)

 Constraint Constraint is a measure of the reduction of variety or reduction of freedom Constraint on this product space can thus represent the mutual dependency between the states of the subspaces, like in the berry example, where the state in the color space determines the state in the size space, and vice versa. Variety and its complement, constraint, can be generalized to a probabilistic framework, where they are replaced respectively by entropy and information. pespmc1.vub.ac.be /CONSTRAI.html   (288 words)

 PostgreSQL: Documentation: Manuals: PostgreSQL 7.4: Constraints We say that the first two constraints are column constraints, whereas the third one is a table constraint because it is written separately from the column definitions. Unique constraints ensure that the data contained in a column or a group of columns is unique with respect to all the rows in the table. In general, a unique constraint is violated when there are (at least) two rows in the table where the values of each of the corresponding columns that are part of the constraint are equal. www.postgresql.org /docs/7.4/static/ddl-constraints.html   (1754 words)

 Constraint-Directed Scheduling   (Site not responding. Last check: 2007-10-07) A problem topology is represented by a constraint graph where nodes are activities and arcs are constraints among the activities, e.g., temporal and resource. Problem textures are fundamental measures of constraint graphs that indicate decision complexity, uncertainty and elasticity. are used to determine where in the constraint graph the next decision is to be made, i.e., variable and constraint selection. www.eil.utoronto.ca /scheduling/chs   (234 words)

 Cork Constraint Computation Centre, University College Cork Constraints arise in design and configuration, planning and scheduling, diagnosis and testing, and in many other contexts. The Cork Constraint Computation Centre (4C) was established at University College Cork with initial funding from Science Foundation Ireland in the form of a Principal Investigator Award to the Centre Director, Science Foundation Ireland Research Professor Eugene C. Freuder. Constraint programming already has wide commercial application, but much remains to be done to fully explore and exploit the technology. 4c.ucc.ie /web/index.jsp   (445 words)

 HAL home page HAL is a strongly typed, weakly moded, constraint logic/functional language designed to support the construction and extension and use of new constraint solvers being developed jointly at the University of Melbourne and Monash University. They had a fixed underlying solver for each constraint domain which was viewed as a closed ``fl box.'' Second generation CLP languages, such as clp(fd) [Diaz and Codognet 93], provided more support by viewing the solver as a ``glass box'' which the programmer could extend to provide problem-specific complex constraints. Constraint solving in CIAO is inherited from the underlying \&-Prolog/SICStus Prolog implementation: solvers are written using attributed variables. www.csse.monash.edu.au /~mbanda/hal   (2833 words)

 Book and Course in Constraint Programming and Reasoning Constraints are formalized as distinguished, predefined predicates in first-order predicate logic. Constraint solving algorithms are specified and implemented in the constraint handling rules language (CHR) in a uniform high-level executable notation. The most common constraint domains, their solvers and applications such as Boolean constraints for circuit design, terms and trees for unification, linear polynomial equations for financial and engineering applications and finite domains for scheduling, are presented. www.informatik.uni-ulm.de /pm/mitarbeiter/fruehwirth/pisa   (720 words)

 A Constraint-Guided Web Walker Circumstance constraints recursively examine the constraints they contain to compute an efficiency sort key, which is the most expensive constraint they scope. Constraint sets are ordered only once; thereafter they can be applied to enumerated URIs without further reordering because the efficiency characterization is independent of the actual resources. In Figure 1, a conditional constraint is used to suppress any HTML resources which were created before January 1, 1996 (specified in seconds since 1900). www.ai.mit.edu /projects/iiip/doc/cl-http/w4/w4.html   (4224 words)

 Constraint Grammar (CG-2) page   (Site not responding. Last check: 2007-10-07) The development of the constraint grammars started in late 1980's, and the first robust version was built in Esprit II project (1989-1992). Later, the ENGCG syntax was essentially rewritten by Timo Järvinen in the Bank of English project (1993-1995) where 200 million words were analysed using the ENGCG. Constraint grammar as a framework for parsing running text. www.ling.helsinki.fi /~tapanain/cg   (295 words)

 Constraint.Satisfaction A positive constraint between two elements can be satisfied either by accepting both of the elements or by rejecting both of the elements. Advocates of coherence theories of truth have often been vague about the constraints, but entailment is one relation that furnishes a positive constraint and inconsistency is a relation that furnishes a negative constraint (Blanshard, 1939). On their account, the elements are actions and goals, the positive constraints are based on facilitation relations (action A facilitates goal G), and the negative constraints are based on incompatibility relations (you cannot go to Paris and London at the same time). cogsci.uwaterloo.ca /Articles/Pages/Cohere.Constrain.html   (8337 words)

 Constraint Programming That is, as soon as a solution is found, a further constraint is added to the effect that the value of the optimizing criterion must be less than the value just found. Constraints have been used in a wide variety of scheduling applications, including vehicle scheduling [Duncan 95], workforce scheduling [Kusumoto 96], container port planning [Parrett 91], and frequency assignment problems [Carlsson 93]. In a GA these would simply be part of the evaluation function, but in a constraint system one at least has the possibility of directly modelling preferences as soft constraints, and of controlling which ones are relaxed. www.aiai.ed.ac.uk /links/constr.html   (1322 words)

 STIP/TIP Fiscal Constraint Worksheets - Planning - HEP - FHWA   (Site not responding. Last check: 2007-10-07) The purpose of these fiscal constraint requirements is to ensure that planning and programming are meaningful, based on realistic assumptions about funding all capital, operating, and maintenance costs associated with the surface transportation system. Fiscal constraint also helps clarify what is possible with existing funding sources, and can inform debate about the need for new funding sources. There are no changes to the requirements for fiscal constraint in the pending bills in the House and Senate, but it may be appropriate to refine this guidance based on other changes to planning requirements. www.fhwa.dot.gov /planning/fcindex.htm   (523 words)

 An Electronic Primer on Geometric Constraint Solving   (Site not responding. Last check: 2007-10-07) In this primer, a solution to the problem of finding a configuration for a set of geometric objects which satisfies a given set of constraints between the geometric elements is detailed. This tour presents the theoretical and technical aspects of our constraint solver which are necessary in order to be able to implement a constraint solver similar to ours. The first version of the constraint solver was implemented in collaboration with Jiazhen Cai and Robert Paige from New York University. www.cs.purdue.edu /homes/cmh/electrobook/intro.html   (308 words)

 Constraint Solver The constraint solver is a protocol security analyzer implemented in Prolog and documented in "Constraint Solving for Bounded-Process Cryptographic Protocol Analysis," presented at CCS-8 ([MS01] in the bibliography, postscript downloadable from the main CAPSL page). The version of the constraint solver in the file csolve.P is slightly extended beyond what is described in the CCS-8 paper. In the B-strand, the principals A and B have been instantiated by constants a and b to ensure that the confidential nonce nb originated in that strand was not intended to be shared with a principal under the control of the attacker. www.csl.sri.com /users/millen/capsl/constraints.html   (1924 words)

 Constraint-Based Languages and Environments for Building Interactive Systems Other constraint satisfaction algorithms developed as part of this project include SkyBlue (for local propagation constraints), Ultraviolet (a hybrid solver that supports subsolvers for different kinds of constraints), and a batch compiler based on Fourier elimination that produces very efficient code for simultaneous linear equalities and inequalities. It is useful to extend the basic notion of constraints to that of a constraint hierarchy: a collection of constraints, some of which must hold, and some of which are preferences but not requirements. In addition, a frequent application of constraint hierarchies is to express the desire that objects in an interactive display not move unless there is some stronger constraint that forces them to do so. cslu.cse.ogi.edu /nsf/isgw97/reports/borning.html   (891 words)

 Logilab.org - Constraint   (Site not responding. Last check: 2007-10-07) This package is a constraint satisfaction problem solver written in 100% pure Python. Constraints and Domain implementations are provided to work with finite domains and finite intervals. It should be fairly easy to add new kind of domains such as finite integer domains, together with specialized constraints. www.logilab.org /projects/constraint   (99 words)

 Advanced Constraint Techniques for User Interface Implementation Constraints as a general computational technique allow the declaration of a set of relationships that are to hold between entities. Constraint systems have been used successfully in interactive systems beginning with some of the earliest work in graphical interfaces [9]. Multi-way constraint systems on the other hand allow a more general form of constraint where information may flow in different directions at different times. cslu.cse.ogi.edu /nsf/isgw97/reports/hudson.html   (1216 words)

 Citations: Constraint Programming - Saraswat, van Henterrynck (ResearchIndex)   (Site not responding. Last check: 2007-10-07) GNU Prolog compiles nite domain constraints in the same way as its predecessor clp(FD) described in [5, 6] It is based on the so called RISC approach which consists in translating at.... Constraints are used to state goals, or more exactly partial goals, that the agent has to achieve. Several efficient constraint solving systems for finite domain constraints now exists, such as Ilog Solver on the commercial side and GNU Prolog on the academic freeware side. citeseer.ist.psu.edu /context/1676865/0   (707 words)

 OUCL Constraints Research Group In any constraint satisfaction problem there is a collection of variables which all have to be assigned values, subject to specified constraints. The constraints group at Oxford is led by Professor Peter Jeavons. Problems with constraints are generally hard to solve efficiently, but we have shown that mathematical properties of the constraints can be used to identify special classes that are easier to solve. web.comlab.ox.ac.uk /oucl/research/areas/constraints   (833 words)

 Foundations of Constraint Satisfaction   (Site not responding. Last check: 2007-10-07) Constraint satisfaction is a general problem in which the goal is to find values for a set of variables that will satisfy a given set of constraints. It is the core of many applications in artificial intelligence, and has found its application in many areas, such as planning and scheduling. This book is the most comprehensive book on the field of constraint satisfaction so far. cswww.essex.ac.uk /CSP/edward/FCS.html   (239 words)

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