On the basis of the present development process for control-unit functions, this paper sets out to discuss various problem areas which have considerable effect on the quality of the function representation in the control unit, as well as on the development time and the number of recursions. A significant aspect of this is the cooperation between function developers and control-unit developers, where it is shown that problems of language and understanding represent fundamental causes of difficulty. Neither is their always complete harmony in practice in the understanding between developers of methods and tools, and the user who employs these tools.A development process is derived on the basis of this analysis with the primary aim of promoting efficient cooperation between function and control-unit developers, but which will also effectively include method and tool development.The underlying philosophy in this is to produce fully tested function specifications before the function is implemented in the control unit. This is intended to give both the control-unit developer and the function developer the freedom to concentrate exclusively on his own development field. It will be shown how the situation can be achieved where the development partners do not need to be constantly waiting for one another in the event of functional modifications. This paper also discusses the importance of trial experiments defined as early as the function specifications, in order to assist the function verification of the finished control unit. In this respect, it will be suggested that the understanding of roles in the implementation of a tool-assisted development process must have a clearly defined interface between tool development and the needs of the user. A tool-assisted development process in a major industry can only be established if various tool modules are mutually compatible on the basis of interface standards and if adequate market support of the tool manufacturer exists.In conclusion, the Outlook covers an aspect which deals with the effects on the cooperation between vehicle manufacturer and supplier. This will indicate the importance of early agreement on concepts which will efficiently allow the exchange of model modules independent of any given tool.