Different notions of function: results from an experiment on the analysis of an existing product

Abstract

Academic debate has long recognised that function is a problematic concept, for which many different notions exist. While progress has been made in relating these different notions theoretically, designers in practice still struggle with the concept of a function and a functional breakdown, even though these ideas form a key part of many established design methodologies. This paper describes the findings of an experiment which explores how different engineers understand the notions of function and functional breakdown in the context of design by modification. The experiment was conducted with a group of 20 design engineers, who had all received or provided the same education at the Karlsruhe Institute of Technology. A second experiment was run with a group of 18 engineers at another university. The subjects were asked to analyse how a hydraulic pump works, summarising their understanding in a function tree. The findings demonstrate the fluidity of notions of function between different individuals expressing both goals and behaviour as functions. Many participants had a syntactic notion of function, expressing functions as verb–noun pairs, but failed to apply this consistently. These observations highlight the need for pragmatic approaches for handling the concept of function.