An `AI in Design' View of Design
Methodology

Control

How is the development of the design guided and controlled?

e.g., through decomposition processes, by task scheduling, by data availability, etc.

Discussion. The control techniques determine the set of actions and their ordering during design development. This is done according to principles which vary by the problem type. There are design problems in which the decomposition of the problem parallels the decomposition of the design (structural, functional, etc.). This latter decomposition can be used as guidance for sequencing the phases of the design process [Liu & Brown 1994]. Other types of design problems can be seen as a set of tasks which have to be carried out [McDermott 1982]. A task scheduler will order these tasks based on some dependencies or priorities, or based on situation recognition.

What are the heuristics used?

e.g., priorities, dependencies, utilities, rationale, etc.

Discussion. The choices made in the control process are guided by heuristics. Heuristics are appropriate as in design the search spaces are usually very large, and any knowledge that can be used to reduce the search (even if it may not always work) should be taken advantage of. Heuristics consist of criteria used to generate, select or order problem-solving steps. Priorities determine a rating of the actions based on some importance measure. Dependencies are used to schedule the control flow such that actions are executed before other actions which depend on them. Utilities can influence the control by evaluating the degree to which some design needs are satisfied by the proposed action, while rationale provides argumentation for or against an action.

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