Bjorn Freeman-Benson, Molly Wilson, and Alan Borning. DeltaStar: A general algorithm for incremental satisfaction of constraint hierarchies. In Proceedings of the 11th Annual IEEE Phoenix Conference on Computers and Communication, pages 561-568, March 1992.  Home/Search   Document Not in Database   Summary   Related Articles   Check

.... that returns 0 if the considered constraint is satis ed and 1 if it is not, many algorithms for solving static hierarchies are known [11 13] The only algorithms known to the author for constraint hierarchies based on nontrivial error functions are either based on the constraint solver DeltaStar [4] or on his own work [17] While the rst approach solves hierarchies of real valued equalities and inequalities, the other solves hierarchies of equalities and inequalities over nite domains. Nevertheless, practical problems are dynamic problems because requirements change. Thus, some ....

Bjorn Freeman-Benson, Molly Wilson, and Alan Borning. DeltaStar: A general algorithm for incremental satisfaction of constraint hierarchies. In Proceedings of the 11th Annual IEEE Phoenix Conference on Computers and Communication, pages 561-568, March 1992.

....solvers must address and some of the approaches for remaining efficient are similar. Constraint systems for interactive graphics must deal with under constrained systems. An under constrained system has remaining degrees of freedom so multiple possible solutions exist. Constraint hierarchies [14, 17, 48] provide a popular and well studied means of removing ambiguity by over constraining the system with constraints at decreasing levels of preference (see Section 2.2) A related concern for solvers is to maintain spatial stability of the system. When a geometric system is under constrained, ....

....aspects of the solver s behavior. For example, the user textually orders the listing of the satisfaction methods to indicate which assignment should be performed when multiple possibilities exist. This type of meta constraint was later replaced by the now classic notion of a constraint hierarchy [17, 48] where constraints may be specified at multiple levels of preference. 7 7 The DeltaStar solver shown in Figure 2.1 was designed simply to aid research in constraint hierarchies by parame 24 x1 x2 r m x1 x2 r m C1 C4 C3 C1 C4 C3 Figure 2.6: Two possible plans for executing Figure ....

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Bjorn Freeman-Benson, Molly Wilson, and Alan Borning. DeltaStar: A general algorithm for incremental satisfaction of constraint hierarchies. In Eleventh Annual International Phoenix Conference on Computers and Communications, pages 561--568, Phoenix, Arizona, April 1992.

....if certain other parts of the computation, further to the right in the tree, would be infinite. An implementation of UCB could not tolerate such a situation. However, we feel that this advantage is not sufficiently important to override our other concerns. 3.5. 2 Implementations of HCLP DeltaBlue [29, 67] and SkyBlue [66] are designed for an HCLP approach to user interface construction and are efficient for repeated solving of a relatively simple set of constraints (e.g. when a mouse moves the end of a line) But DeltaBlue cannot cope with multiple output variables or with cycles (see below) and ....

....unusably inefficient. Both HCLP and PCSP are so general that it is possible to imagine parameters that would make them inefficient, for example a poor choice of comparator or distance function. But both of them have instances which have already been implemented in a sufficiently efficient manner [29, 33, 60]. Indeed Sannella has produced the SkyBlue system which contains an HCLP solver sufficiently efficient to be used for interactive graphics [66] Gocs, our framework for preference systems which can combine all the advantages of HCLP and PCSP, is more general than HCLP and PCSP, and so poor choices ....

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Bjorn Freeman-Benson, Molly Wilson, and Alan Borning. DeltaStar: A General Algorithm for Incremental Satisfaction of Constraint Hierarchies. In Proceedings 11th IEEE Phoenix Conference on Computers and Communications, pages 561-- 568, Scottsdale, Arizona, April 1992.

....constraint solvers must address and some of the approaches for remaining e#cient are similar. All constraint systems must deal with under constrained systems. An under constrained system has remaining degrees of freedom remain so multiple possible solutions exist. Constraint hierarchies [BMMW89, FBWB92] provide a popular and well studied means of removing ambiguity by over constraining the system with constraints at decreasing levels of preference. Then a simple greedy algorithm permits using just enough constraints to maintain a fully specified system and a unique solution. An alternative ....

....the solver s behaviour. For example, the user textually orders the listing of the satisfaction methods to indicate which assignment should be performed when multiple possibilities exist. This type of meta constraint was later refined into the now classic notion of a constraint hierarchy [BMMW89, FBWB92] where constraints may be specified at multiple levels of preference. 11 Blue is a multi way LP solver that respects constraint hierarchies by finding the best solution [FBMB90] Best is defined in terms of comparators. Blue uses the locally predicate better notion to compare two solutions ....

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Bjorn Freeman-Benson, Molly Wilson, and Alan Borning. DeltaStar: A general algorithm for incremental satisfaction of constraint hierarchies. In Eleventh Annual International Phoenix Conference on Computers and Communications, pages 561--568, Phoenix, AZ, April 1992.

.... about the error in satisfying it information not conveniently available from CLP(R) The second interpreter is thus implemented in Common Lisp, and has to do much more of the work itself (such as keeping track of backtracking information) The interpreter uses an incremental algorithm, DeltaStar [21, 22], to find solutions to constraint hierarchies. DeltaStar is actually a family of algorithms, parameterized by an underlying flat constraint solver (i.e. one that solves a collection of required constraints) The key procedure that the flat solver must provide is filter: filter( S : Solution, C ....

Bjorn Freeman-Benson, Molly Wilson, and Alan Borning. DeltaStar: A General Algorithm for Incremental Satisfaction of Constraint Hierarchies. In Proceedings of the Eleventh Annual IEEE Phoenix Conference on Computers and Communications, pages 561--568, Scottsdale, Arizona, March 1992. IEEE.

....or partial order. The solutions to a constraint hierarchy are the valuations (mappings from variables to values) that best satisfy the constraints in the hierarchy, respecting their relative strengths. References [6, 18] present a formal description of the theory of constraint hierarchies, while [16, 17] describe two algorithms, DeltaBlue and DeltaStar respectively, for finding solutions to them. Extending the Celsius Fahrenheit Kelvin example with a constraint hierarchy results in the constraint graph: G = 8 : required c 3 1:8 = f 0 32:0 required c = k 0 273:13 strong c = 0:0 ....

Bjorn Freeman-Benson, Molly Wilson, and Alan Borning. DeltaStar: A General Algorithm for Incremental Satisfaction of Constraint Hierarchies. In Proceedings of the Eleventh Annual IEEE Phoenix Conference on Computers and Communications, pages 561--568, Scottsdale, Arizona, March 1992. IEEE.

....can solve constraint hierarchies consisting of arbitrary collections of linear equality and inequality constraints using the weighted sum metric better, worst case better, and locally metric better comparators. These algorithms are instances of our general DeltaStar [Freeman Benson Wilson 90, Freeman Benson et al. 92] framework and are collectively referred to as the Orange algorithms. The DeltaStar framework is an algorithm for incrementally solving a constraint hierarchy, based on an alternate, but provably equivalent, description of the constraint hierarchy. DeltaStar is actually a family of algorithms, ....

Bjorn Freeman-Benson, Molly Wilson, and Alan Borning. DeltaStar: A General Algorithm for Incremental Satisfaction of Constraint Hierarchies. In Proceedings of the Eleventh Annual IEEE Phoenix Conference on Computers and Communications, Scottsdale, Arizona, March 1992. IEEE.

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Freeman-Benson, B., Wilson M., Borning A. 1992 Delta Star: A General Algorithm for Incremental Satisfaction Of Constraint Hierarchies, In Proceedings of the Eleventh Annual IEEE Phoenix Conference on Computers and Communications, Scottsdale, Arizona, March, pp 561-568.

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