Toward Design as Collaboration

In design, multiple disparate goals must be addressed simultaneously. It is the thesis of this work that problems in two-dimensional layout design can be solved by collaboration among single-goal, intelligent agents, each responsible for a class of objects and responsive to explicit metrics. In this model, each agent produces conflict-free designs for its own class of objects, and then, when objects conflict with each other in the combined design, the agents that own those objects address the conflicts. A limitedly rational implementation demonstrates its efficacy for park layout design in the two-dimensional plane. Two-dimensional Layout Design Design problems typically entail large search spaces and multiple, ill-defined goal tests (Goel and Pirolli 1989). As a result, design has been regarded as a domain (CAD/ CAM) in which computers assist people rather than work alone. This paper’s primary contributions are a model for autonomous two-dimensional layout design as collaboraCopyright  1998, American Association for Artificial Intelligence (www.aaai.org). All rights reserved. tion among a set of agents, and a limitedly rational architecture for this model. Drawing upon research on human experts, the model devotes considerable effort to the selection of an initial high-quality state likely to include multiple constraint violations, and then seeks to remove them. The problem in two-dimensional layout design is to position a set of two-dimensional objects within a prespecified outline to meet a set of restrictions (criteria). In the park design problem of Table 1, for example, 13 objects must be located precisely on a grid. Criteria that must be satisfied are called constraints. In Table 1, only the object criteria and C5 are constraints. Table 1’s task is non-trivial; about 1.3 × 1026 placements abide by the object constraints. A solution to a two-dimensional layout design problem positions all the objects and satisfies all the constraints. Typically there are many solutions; it is the multiple, vague goal tests make design problems particularly difficult (Goel and Pirolli 1992). Those tests are represented here as non-required criteria called principles. (There are 7 in Table 1.) Principles are important to a designer, but in some unspecified combination. As a result, design is not an optimization problem, yet designers speak of solutions that are “better” or “worse” (Goel and Pirolli 1992). Thus in a Table 1: A park design problem. Task: Place on a 20 × 40 discrete grid the following objects: PF1: a 7 × 7 playing field P1: a 5 × 3 pond B1: a 5 × 10 building F1: a 6 × 7 forest R1: a road of width 1 PF2: a 5 × 2 playing field P2: a 3 × 2 pond B2: a 2 × 2 building F2: a 4 × 2 forest R2: a road of width 1 PF3: a 5 × 2 playing field R3: a road of width 1 R4: a road of width 1 Goal: Satisfy all constraints and respond to all principles as well as possible. Object constraints: PF1 boundary is ≥ 0.1 away from all edges. PF3 center is within 0.8 of the park’s center. B1 boundary is against some edge. B2 center is within 0.5 of the park’s center. P1 boundary is ≥ 0.3 away from all edges. P2 center is within 0.3 of the park’s center. F1 center is within 0.4 of the park’s center. F2 boundary is within 0.1 of some edge. R1 runs from the eastern grid edge. R2 runs from the western grid edge. R3 runs from the northern grid edge. R4 runs from the southern grid edge. R1, R2 , R3 , and R4 are connected. Intra-class principles: C1: Total road length should be small. C2: Fields should not adjoin each other. C3: Ponds’ centers should be ≤ .2 of the grid apart. C4: Buildings’ centers should be ≤ .6 of the grid apart. Inter-class constraint: C5: Objects may not overlap. Inter-class principles: C6: Buildings should be adjacent to roads. C7: Every building should have a view, i.e., be within 2 units of a pond or forest. Secondary inter-class principle: C8: Minimize the total Manhattan distance of all empty grid positions to their nearest road. From: AAAI-98 Proceedings. Copyright © 1998, AAAI (www.aaai.org). All rights reserved.