Navigation within a structured search space in layout problems

HeGeL-2 is a heuristic-based layout generator equipped with a nonserial dynamic programming algorithm. HeGeL-2 finds optimal solutions to plan-layout design (PLD) problems which are defined as problems that involve the allocation of a nontrivial number (ten or more) of design units in one application. The search strategy HeGeL-2 uses is similar in some respects and dissimilar in others to human search behavior, which has been simulated in an earlier version of HeGeL-2. These similarities include constraint relaxing strategies common to both versions. Dissimilarities concern claims of optimality and 'goodness' of solutions measured by an objective function based on soft constraints. In this paper, the general problem of navigation in a search space for layout problems is discussed in the context of a general-purpose formalism. Through this formalism several layout generators, including LOOS, WRIGHT, and HeGeL-2, are described.