" INTERNATIONAL CONFERENCE ON ENGINEERING DESIGN ICED'93 THE HAGUE, AUGUST 17-19 1993 TOWARDS A THEORY FOR FUNCTIONAL REASONING IN DESIGN Amaresh Chakrabarti ABSTRACT Engineering design can be considered a problem solving activity where a designer starts with functional descriptions of the problem (ie, what the intended product should do), and undergoes a reasoning process, co-evolving both the problem and its possible solutions, aimed at eventually producing a solution in terms of its realisable form (structural) descriptions, Reasoning about design problems and solutions in terms of their functionality, termed here as functional reasoning, is central to designing. Therefore, problem, solution, function and form are important concepts in design, and devising ways for supporting functional reasoning is important. Supports for functional reasoning should include supports for (i) representation and change of design problems and solutions, (ii) generation of problems that a given solution could solve, and (iii) generation of solutions to a given problem. As a prerequisite to supporting functional reasoning, an understanding of (i) the above concepts, and (ii) the processes for functional reasoning is required. How functional reasoning is done is largely dependent on (i) how the knowledge about functions, form and their relations are gathered represented, and (ii) how a design problem and its possible solutions are understood in terms of this knowledge of function and form, and are used in problem solving. All these could probably form part of a theory for functional reasoning. The feasibility and scope of such a theory would depend on whether we could find measurable criteria to define function, form, problems and solutions in the design context. This paper provides a survey of literature in design research to highlight the multiplicity of views about the above concepts, and examines the feasibility, scope, goals, possible approaches, and validation issues for producing a testable theory for functional reasoning. INHAL TSANGABE KEYWORDS Engineering Design Theory, Functional Reasoning, Functional Synthesis, Design Automation, Function-Form Relationships in Design 1 INTRODUCTION Engineering design can be considered a problem solving activity [1] where design problem and its solutions co-evolve. A designer starts with functional descriptions of the problem (ie, what the intended product should do), and undergoes a reasoning process aimed at eventually producing a solution in terms of its form (structural) descriptions from which the solution can be realised. Reasoning about design problems and solutions in terms of their functionality, termed here as functional reasoning, is central to designing. Therefore, problem, solution, function and form are important concepts in design, and devising ways for supporting functional reasoning is important. As a prerequisite to supporting functional reasoning, an understanding of (i) the above concepts, and (ii) the processes for functional reasoning is required. This article attempts to highlight the multiplicity of views about these issues, and examines the possibility, goals and possible approaches to produce a theory offunctional reasoning. The next section provides a background to the present state of understanding of these issues; from this, the possible supports to, and as a pre-requisite to these, the goals and scope for a possible theory for functional reasoning are outlined in section three. Finally, the issue of validating any such theory is discussed in section four.