Some Ontological Distinctions of Function Based on the Role Concept

Function is an important aspect of artifacts in engineering design. Although many definitions of function have been proposed in the extensive research mainly in engineering design and philosophy, the relationship among them remains unclear. Aiming at a contribution to this problem, this paper investigates some ontological issues based on the role concept in ontological engineering. We discuss some ontological distinctions of function such as essentiality and actuality and then propose some fundamental kinds of function such as essential function and capacity function. Based on them, we categorize some existing definitions in the literature and clarify the relationship among them. Then, a model of function in a product life-cycle is proposed. It represents the changes of existence of the individuals of each kind of function, which are caused by designing, manufacturing and use. That model enables us to give answers to some ontological questions such as when and where a function exists and what a function depends on. The consideration on these issues provides engineers with some differentiated viewpoints for capturing functions and thus contributes to consistent functional modeling from a specific viewpoint. The clarified relationships among the kinds of function including the existing definitions in the literature will contribute to interoperability among functional models based on the different kinds and/or definitions.