Abstract
The value of the artifact is evaluated by the users’ subjective, which is called value-in-use. To improve value-in-use, designers need to enhance value-related functions and eliminate redundant behaviours unrelated to value. However, the functions and behaviours that users perceive vary depending on circumstances. To realise the high value-in-use, designers need to repeatedly reflect and redefine information on value-in-use into design specifications by observing the circumstances where users receive functions and behaviours. Further on, according to previous studies, functions and value-in-use are defined respectively, but the relationship between the two is unclear. Thus, it is difficult for designers to understand what functions and behaviours users perceive in artefacts and how they are related to the value-in-use. Based on the above considerations, this paper clarifies the relationship between functions and the value-in-use by organising their fundamental concepts. Furthermore, this paper supports designers in redefining their design specifications based on information related to value-in-use by making it possible to describe and acquire that information. Specifically, reviews of existing research on functions and value-in-use clarify the three problems with the authors’ conventional definitions. Then, this study addressed these problems by modifying the definitions and utilising a case study to confirm that the modified definitions were indeed valid and effective in addressing the problems.
