The value and limitations of using process models to describe the manufacturing organization

Process models offer a systematic, well-denned way of representing the structure of a firm's manufacturing operations. They record the activities that are performed in order to achieve a well-defined purpose of some kind (especially a commercial one), together with the activities' inter-dependencies. In notations such as that of IDEF_o these models have a hierarchical decomposition, in which activities are successively decomposed into more detailed activities, connected by a pattern of constraints of various kinds. Process models can be used to substantiate a number of claims about the satisfactoriness of a firm's operating structures: claims that its activities can be carried out with a greater degree of concurrency, for instance, or that there are redundant or duplicated activities, or spans of control that do not match readily-identified processes. This paper describes a number of observations that were made about the practice of process modelling in an engineering firm. It discusses, in particular, the limited expressive power of process modelling notations and the problems encountered when a normative approach is taken to the analysis of a model-when the analysis refers to some notion of an ideal factory (such as a cellular organization).