INTERNATIONAL CONFERENCE ON ENGINEERING DESIGN ICED 99 MUNICH, AUGUST 24-26, 1999 TOWARDS A FORMAL THEORY OF PRODUCTS INCLUDING MEREOLOGY Filippo A. Salustri and Jeffrey C. Lockledge Keywords: formal logic, mereology, product model 1 Introduction Ontology is the branch of logic dealing with the nature of what is. In recent years, ontology has been used to attempt to formalize various aspects of engineering design. These efforts have focussed on the application of taxonomy to categorize design knowledge based on the properties of entites, and have led to new artificial intelligence technologies that are finding application in industrial settings. However, the related field of mereology, which treats parts and wholes, has been neglected. The distinction between taxonomy and mereology may seem subtle but is fundamental; in a conventional taxonomy, a car would typically be represented with the property of having four wheels; mereologically, however, a relation would exist between the car and its wheels. In a purely merelogical perspective, the most fundamental predicate is part-of (part, whole), a binary relation mapping part/whole pairs to boolean values, whereas in a taxonomic perspective, the fundamental predicate is is-a(instance, type), which maps instance/type pairs to boolean values. While it might seem natural for engineers and engineering researchers to be interested in mereology as well as taxonomy, there is no work on the subject in the recent engineering literature of which the authors are aware. Most of the reported work appears to have been carried out by philosophers, cognitive scientists, and artificial intelligence researchers. While this research is important, its focus has been on representing common sense notions of parthood that the average non-engineer might hold. Although engineers will claim common sense as a valuable tool, it is a common sense resulting from years of technical education and experience, and is quite dissimilar from that of the lay person. Therefore, it seems reasonable that a mereology developed specifically for engineering will differ substantially from those developed for other domains. Indeed, this sentiment is also expressed by Artale et al [1]. There are many different kinds of part/whole relations; some examples include: • a feature can be part of an object, and a component can be part of an assembly; • a bolt holding two parts together is a part itself, but having the special status of a fastener; • an item may be a part of a batch, or a part of an assembly; and • the driver of an automobile may be considered a part of a car, but not in the same way as a wheel is a part of a car.