Pineda, Luis A.2014-10-212014-10-2119921467-8659https://doi.org/10.1111/1467-8659.1130333In this paper we discuss two kinds of constraint satisfaction problems that arise in the context of geometric modelling, In particular in the modification of 2-D wire-frame diagrams that are subject to an arbitrary number of geometrical and topological constraints. We argue that problems in this domain can be classified in two categories that we shall call problems of reference and problems of synthesis. Since Sutherland s Sketchpad program [16], a large number of systems have addressed constraint satisfaction in terms of the representation of constraints sets as equation systems, which in turn are solved by numerical methods like local propagation, relaxation and Gaussian elimination. Here, we present an alternative framework. We argue that conceptualising constraint satisfaction as symbolic rather than"numerical" problems helps to clarify the notion of"constraint", simplify solution methods, and to explain the intuitive inferential processes underlying the modification of drawings in the course of interactive drafting sessions. The theory presented in this paper has been tested with an experimental computer program called Graflog [5, 8, 9, 10, 11, 12]. The program has been implemented during the last four years, and has evolved through several stages. The current version is implemented in terms of two Unix-processes connected by Unix-pipes. The first is a"C" program running X windows, and handles the external aspects of the interaction. The second is a Prolog program supporting the representational structures and interpreters of the system.10.1111/1467-8659.1130333333-344