Michael R. Wilk. "Equate: An Object-Oriented Constraint Solver". Sigplan Notices 26, 11 (Nov. 1991), 286-298. ACM Conference on Object-Oriented Programming Systems, Languages, and Applications; OOPSLA'91.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....set of algebraic constraints, exploits a more elaborated approach of replacing cycles through algebraic transformations. General constraint languages based on term rewriting solvers have also been used in the context of graphical applications, for example the systems Bertrand [Leler, 1988] Equate [Wilk, 1991] , and Siri [Horn, 1992] Geometric solvers Here, we point to the so called geometric constraint engine by [Kramer, 1992] which provides a geometric constraint solver that allows direct inferences along DOFs of geometric entities. Domain specific solvers Many graphics and visualization systems ....

M. R. Wilk. Equate: An object-oriented constraint solver. In A. Paepcke, editor, Proceedings of OOPSLA '91 (ACM Conference on Object-Oriented Programming Systems, Languages, and Applications), pages 286--298. ACM Press, New York, NY, October 1991.

....is similar to the pre and postcondition facilities in Go [5] It is limited to constraint maintenance (i.e. truth maintenance, as opposed to starting with an inconsistent situation that is then resolved) and not further considered in this paper. A more powerful technique is presented in [23]. There, the constraint solver produces a set of programs that solve constraints which are stated in the form of equations. It translates a declarative constraint equation into procedural solutions in terms of messages back to objects. The problem is the local character of the solution. More ....

....by n unary constraints to constrain the endpoints of a rod to lie on walls. The total number of constraints is thus n q m. The complexity for RX is then O(m(q m n) For CP 3, the number of constraints increases to n m, resulting in a complexity of O( m n) 9 Equate and OOCS Equate [23] is a constraint satisfaction system that uses term rewriting as a guide to find solutions. Constraints are specified as equations. Rewrite rules convert equations into equivalent sets of equations that can more easily be solved. This repeats recursively (zero or more times) until equations are ....

Michael Wilk. Equate: an object-oriented constraint solver. In Proceedings OOPSLA '91, pages 286--298, 1991.

....San93] However, constraints are not expressed in terms of object interactions, so some inter object dependencies are difficult to express as constraints between instance variables. Moreover, some limitations on types of components are imposed by the constraint solver. Finally, as Wilk said in [Wil91] Encapsulation was violated by the constraint expressions . 5 Conclusion flo language is an object oriented language, implemented with stklos [Gal94] integrating the concept of dependencies in a declarative way. The user can define dependencies, declare dependencies between objects and the ....

Mickael R. Wilk. Equate: An object-oriented constraint solver. In Proceedings of OOPSLA'91, pages 286--298. ACM, 1991.

....to allow multiple solutions is also discussed, which would allow Betrand retaining the expressive power of LP. The extensions of Bertrand mimic what is already present in LP: the equality theory for unification of Herbrand terms and local variables. The object oriented language extension EQUATE [Wil91] simplifies arithmetic constraints into a sequence of procedural solution steps. EQUATE uses rewrite rules, which can be seen as LP rules. The procedural solutions use destructive assignment, thus an ordering has to be imposed on the solutions steps to avoid read write conflicts. The approach has ....

M. R. Wilk, Equate: An Object-Oriented Constraint Solver, ACM OOPSLA 91, 1991, pp 286-298.

....algebraic constraints, exploits a more elaborated approach of replacing cycles through algebraic transformations. General constraint languages based on term rewriting solvers have also been used in the context of graphical applications, for example the systems Bertrand [ Leler, 1988 ] Equate [ Wilk, 1991 ] and Siri [ Horn, 1992 ] 8 you may also consult [Takahashi et al. 1995 ] Geometric solvers Here, we point to the so called geometric constraint engine by [ Kramer, 1992 ] which provides a geometric constraint solver that allows direct inferences along DOFs of geometric entities. ....

M. R. Wilk. Equate: An object-oriented constraint solver. In A. Paepcke, editor, Proceedings of OOPSLA '91 (ACM Conference on Object-Oriented Programming Systems, Languages, and Applications), pages 286--298. ACM Press, New York, NY, October 1991.

....guarded by so called propagators. The propagators send messages to other objects to maintain the constraints. This technique is similar to the pre and postcondition facilities in Go [Dav91] GoP93] This approach is limited to constraint maintenance, starting with a consistent situation. Equate [Wil91] uses term rewriting as a guide to find solutions. Constraints are specified as equations, and rewrite rules convert equations into equivalent sets of equations that can be solved by messages to an object. The rewrite rules which rewrite the equations are provided by the classes and are similar to ....

Michael Wilk. Equate: an object-oriented constraint solver. In Proceedings OOPSLA'91, pages 286--298, 1991.

....variables) and on the other side, the introduction of global resolution mechanism extends the object oriented imperative framework. One of the most important difficulties of these systems is to provide efficient global resolution algorithms. In the constraint object programming approach [3, 8, 13, 19, 24, , constraints are used to automatically and incrementally maintain relations between objects or attributes of objects. In the heart of these systems, there is an incremental constraint solver which is used to permanently ensure the satisfaction of the constraints (if it is possible) The ....

M.R. Wilk : "Equate: An Object-Oriented Constraint Solver", OOPSLA'91, pp. 286-298, 1991.

.... views, liaison between menu and text selection) KR91, San89, CMP91, Rum92] Consequently object systems allying objects and constraints have been developed [MGZ92, FBMB90, Ilo91] For this approach, we need information on object s structures, which goes against principles of object encapsulation [Wil91], and does not allow expression of event based actions. The standard daemon and active value mechanisms allow implementation of certain dependencies, however there is also a diffusion of information and it is not easy to define new dependencies [FPT89] In a class instance model, we allow a ....

M.R. Wilk. Equate: An object-oriented constraint solver. In OOPSLA '91 Proceedings, pages 286--297. ACM, 6--11 October 1991.

.... programming specifies the actions to be taken (imperative programming) while constraint programming specifies a set of constraints that have to be maintained (declarative programming) A number of ways have been tried to combine objects and constraints, see for example [LvdB91] Dav91, GoP93] [Wil91], HB94] These systems often cannot solve global constraints, due to the local character of the satisfaction mechanism. More powerful solutions are necessarily global in nature, potentially breaking the information hiding principle. One way to restrict this, is to have an object allow value ....

Michael Wilk. Equate: an object-oriented constraint solver. In Proceedings OOPSLA'91, pages 286--298, 1991.

....are based on a local propagation of degrees of freedom within the constraint graph, the Delta Blue algorithm is just an incremental version of the Blue algorithm where the constraint graph need not be recomputed from scratch with each removal or addition of a constraint. The algorithm presented in [Wil91] has a better conflict detection that is based on information, provided explicitly by the user. Magritte [Gos83] employs a propagation method to transform the undirected constraint graph and then breadth first search is used to derive all solutions. Constraint Kernels, a system described in ....

Michael R. Wilk. Equate: An Object-Oriented Constraint Solver. In OOPSLA, pages 286--298. ACM, 1991.

....where each variable can be an output. In the context of local propagation for ordinary systems, researchers have been investigated various topics, for example, incremental satisfaction of constraint systems [43, 88] treatment of pointer variables [41, 87] compilation of constraint systems [89], support of computer supported cooperative work [34] and light implementation of constraints [44] Another technique for solving ordinary systems is transformation. GITS uses a simple technique that replaces constraints using a pre defined table [69] The Magritte graphic editor utilizes ....

....of constraints [44] Another technique for solving ordinary systems is transformation. GITS uses a simple technique that replaces constraints using a pre defined table [69] The Magritte graphic editor utilizes algebraic transformation [29] Systems employing term rewriting are also proposed [35, 89]. Depart from GUIs, techniques for solving constraint systems over finite domains have been extensively studied in the context of CSPs [85] Traditional approaches are search techniques such as backtracking and forward checking [85] Recently, problem reduction techniques using arc consistency ....

Wilk, M. R., "Equate: An Object-Oriented Constraint Solver," in Proceedings of the ACM Conference on Object-Oriented Programming Systems, Languages, and Applications (OOPSLA), 1991, pp. 286--298.

....graph rewriting is a fundamentally different execution model from the standard imperative one, bringing this technique in conflict with goal 3. The first programming language to use graph rewriting to integrate objects and constraints is Bertrand [29] later systems of this type are Equate [39], and Siri [20] A primary design goal of Equate is preserving object encapsulation in the internal operation of the constraint satisfier, which, as noted above, we view as an inappropriate goal. Siri has a completely integrated object model similar to that of BETA [27, 26] and thus better ....

Michael Wilk. Equate: An Object-Oriented Constraint Solver. In Proceedings of the 1991 ACM Conference on Object-Oriented Programming Systems, Languages, and Applications, pages 286--298, Phoenix, October 1991.

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Michael R. Wilk. "Equate: An Object-Oriented Constraint Solver". Sigplan Notices 26, 11 (Nov. 1991), 286-298. ACM Conference on Object-Oriented Programming Systems, Languages, and Applications; OOPSLA'91.

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M. R. Wilk, Equate: An Object-Oriented Constraint Solver, ACM OOPSLA 91, 1991, pp 286-298.

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