Model-Based System Architecture, 2nd Edition

17The FAS Method

The functional architecture is often mentioned in publications about systems engineering or in the context of real system projects. On the second view, you will realize that different terms are used for an architecture based on functions like logical architecture, logical view, or functional view. And different artifacts are part of those architectures: sets of functions, flow models, or functional models for simulation purposes. However, they all share the same notion: a technology-independent function-oriented description of the system.

Jesko Lamm and Tim Weilkiens have observed a lack of concrete common methods for functional architectures particularly in model-based systems engineering (MBSE). Some years ago, they described the Functional Architectures for Systems (FAS) method [153]. It was not a complete new method, but more a putting together of already existing puzzle pieces. The FAS method is a practice-proven method based on common MBSE practices.

We describe FAS in this chapter and start with our view on the terminology and motivation of functional architectures. Finally, we shine a light on different aspects of functional architectures like tool support, nonfunctional requirements, functional architectures for cyber-physical systems, and the role of technology in a technology-independent description. Parts of this chapter are based on our article “Method for Deriving Functional Architectures from Use Cases” [154]. We omit the citation of the article ...