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Efficient solving of quantified inequality constraints over the real numbers
 ACM Transactions on Computational Logic
"... Let a quantified inequality constraint over the reals be a formula in the firstorder predicate language over the structure of the real numbers, where the allowed predicate symbols are ≤ and <. Solving such constraints is an undecidable problem when allowing function symbols such sin or cos. In the ..."
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Cited by 26 (7 self)
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Let a quantified inequality constraint over the reals be a formula in the firstorder predicate language over the structure of the real numbers, where the allowed predicate symbols are ≤ and <. Solving such constraints is an undecidable problem when allowing function symbols such sin or cos. In the paper we give an algorithm that terminates with a solution for all, except for very special, pathological inputs. We ensure the practical efficiency of this algorithm by employing constraint programming techniques. 1
Continuous FirstOrder Constraint Satisfaction
 ARTIFICIAL INTELLIGENCE, AUTOMATED REASONING, AND SYMBOLIC COMPUTATION, NUMBER 2385 IN LNCS
, 2002
"... This paper shows how to use constraint programming techniques for solving firstorder constraints over the reals (i.e., formulas in the firstorder predicate language over the structure of the real numbers). More specifically, based on a narrowing operator that implements an arbitrary notion of con ..."
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Cited by 22 (12 self)
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This paper shows how to use constraint programming techniques for solving firstorder constraints over the reals (i.e., formulas in the firstorder predicate language over the structure of the real numbers). More specifically, based on a narrowing operator that implements an arbitrary notion of consistency for atomic constraints over the reals (e.g., boxconsistency), the paper provides a narrowing operator for firstorder constraints that implements a corresponding notion of firstorder consistency, and a solver based on such a narrowing operator. As a consequence, this solver can take over various favorable properties from the field of constraint programming.
Qualitative Decision Making in Adaptive Presentation of Structured Information
 ACM TOIS
, 2003
"... We present a new approach for adaptive presentation of structured information, based on preferencebased constrained optimization techniques rooted in qualitative decisiontheory. ..."
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Cited by 10 (5 self)
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We present a new approach for adaptive presentation of structured information, based on preferencebased constrained optimization techniques rooted in qualitative decisiontheory.
Dynamic approximation of complex graphical constraints by linear constraints
 In Proceedings of the Fifteenth ACM Symposium on User Interface Software and Technology
, 2002
"... Current constraint solving techniques for interactive graphical applications cannot satisfactorily handle constraints such as nonoverlap, or containment within nonconvex shapes or shapes with smooth edges. We present a generic new technique for efficiently handling such kinds of constraints based ..."
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Cited by 8 (4 self)
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Current constraint solving techniques for interactive graphical applications cannot satisfactorily handle constraints such as nonoverlap, or containment within nonconvex shapes or shapes with smooth edges. We present a generic new technique for efficiently handling such kinds of constraints based on trust regions and linear arithmetic constraint solving. Our approach is to model these more complex constraints by a dynamically changing conjunction of linear constraints. At each stage, these give a local approximation to the complex constraints. During direct manipulation, linear constraints in the current local approximation can become active indicating that the current solution is on the boundary of the trust region for the approximation. The associated complex constraint is notified and it may choose to modify the current linear approximation. Empirical evaluation demonstrates that it is possible to (re)solve systems of linear constraints that are dynamically approximating complex constraints such as nonoverlap sufficiently quickly to support direct manipulation in interactive graphical applications. KEYWORDS: Constraintsolving, direct manipulation, trust regions, linearization of constraints, nonoverlap, containment.
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"... do not contain solutions. When we cannot easily prune more elements, we do branching by splitting a bound into pieces (for quantified variables this means replacing subconstraints of the form ∀x ∈ I φ by ∀x ∈ I1 φ ∧ ∀x ∈ I2 φ where I = I1 ∪ I2, or the corresponding existential case). This gives us ..."
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do not contain solutions. When we cannot easily prune more elements, we do branching by splitting a bound into pieces (for quantified variables this means replacing subconstraints of the form ∀x ∈ I φ by ∀x ∈ I1 φ ∧ ∀x ∈ I2 φ where I = I1 ∪ I2, or the corresponding existential case). This gives us new possibilities for pruning. We repeat the two steps until we have pruned all elements (or disproved the constraint). For computing elements of the bounds that do contain solutions we take the negation of the input constraint and again apply the above branchandprune approach. In the paper we formalize this approach, study its properties in detail, improve it for an implementation, and do timings that show its efficiency. As a sideeffect, this paper even improves the current methods for numerical constraint satisfaction problems in the case where the solution set does not consist of finitely many, isolated solutions, which—up to now—was essential for their efficiency. For example, the book describing the system Numerica [56] explicitly states that for inputs not fulfilling that property the method creates
Smooth Linear Approximation of Nonoverlap Constraints
"... Abstract. Constraintbased placement tools and their use in diagramming tools has been investigated for decades. One of the most important and natural placement constraints in diagrams is that their graphic elements do not overlap. However, nonoverlap of objects, especially nonconvex objects, is ex ..."
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Abstract. Constraintbased placement tools and their use in diagramming tools has been investigated for decades. One of the most important and natural placement constraints in diagrams is that their graphic elements do not overlap. However, nonoverlap of objects, especially nonconvex objects, is extremely difficult to solve, especially to solve sufficiently rapidly for direct manipulation. Here we present the first practical approach for solving nonoverlap of possibly nonconvex objects in conjunction with other placement constraints such as alignment and distribution. Our methods are based on approximating the nonoverlap constraint by a smoothly changing linear approximation. We have found that this in combination with techniques for lazy addition of constraints, is rapid enough to support direct manipulation in reasonably sized diagrams. 1
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"... XML addresses several HTML shortcomings, but its underdefined processing impedes the development of adequate generic presentation models for the Web. Such models must define the parsing, validation, transformation and rendering of multilanguage XML documents, according to a variety of adaptation re ..."
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XML addresses several HTML shortcomings, but its underdefined processing impedes the development of adequate generic presentation models for the Web. Such models must define the parsing, validation, transformation and rendering of multilanguage XML documents, according to a variety of adaptation requirements. However, most existing approaches only define subsets of this functionality and do not follow the Web design principles. We hypothesise that generic document presentation can be achieved by utilising the presentation domain constraints and addressing the document processing problem as a whole. This thesis focuses on the document preprocessing domain and supports our hypothesis by proposing a preprocessing framework and the XMLPipe preprocessing model. Document preprocessing is the document presentation subset that only addresses parsing, validation and transformation. The preprocessing framework establishes the necessary preprocessing functionality and enables the evaluation of XMLPipe. XMLPipe utilises the presentation domain constraints to provide generic XML preprocessing.