Geometric problems defined by constraints can be represented by geometric constraint graphs whose nodes are geometric elements and whose arcs represent geometric constraints. Reduction and decomposition are techniques commonly used to analyze geometric constraint graphs in geometric constraint solving.In this paper we first introduce the concept of deficit of a constraint graph. Then we give a new formalization of the decomposition algorithm due to Owen. This new formalization is based on preserving the deficit rather than on computing triconnected components of the graph and is simpler. Finally we apply tree decompositions to prove that the class of problems solved by the formalizations studied here and other formalizations reported in the literature is the same.
We present an approach for handling geometric constraint problems with under-constrained configurations. The approach works by completing the given set of constraints with constraints that can be defined either automatically or drawn from an independently given set of constraints placed on the geometries of the problem. In both cases, the resulting completed set of constraints is not over-constrained. If every well-constrained subproblem in the given underconstrained configuration is solvable, the completed constraint problem is also solvable.
We study the domain of two constructive geometric constraint solving techniques. Both deal with constraints represented by a geometric constraint graph. The first technique analyses the graph bottom-up, from the edges to the whole graph. The second technique analyses the graph topdown, from the whole graph to the individual edges. We describe these techniques using abstract reduction systems which simpli3es the study of their properties. We present an abstract description of the domain of each technique. Finally, we show that both techniques have the same domain, that is, they solve the same kind of problems defined by geometric constraints.
Geometric problems defined by constraints can be represented by geometric constraint graphs whose nodes are geometric elements and whose arcs represent geometric constraints. Reduction and decomposition are techniques commonly used to analyze geometric constraint graphs in geometric constraint solving.In this paper we first introduce the concept of deficit of a constraint graph. Then we give a new formalization of the decomposition algorithm due to Owen. This new formalization is based on preserving the deficit rather than on computing triconnected components of the graph and is simpler. Finally we apply tree decompositions to prove that the class of problems solved by the formalizations studied here and other formalizations reported in the literature is the same.
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