Two Sides of Structuring Multi-Functional Software Systems: Function Hierarchy and Component Architecture

We introduce a theory for the identification, modeling, and formalization of two methodologically essential, complementary views onto software and software intensive systems. One view addresses mainly tasks in requirements engineering when describing the overall system functionality from the users' point of view. By this view we aim at the specification of the comprehensive user functionalities of multifunctional systems in terms of their functions, features, and services as well as their mutual dependencies. This view leads to a function or service hierarchy. The other view essentially addresses the design phase with its task to develop logical architectures formed by networks of cooperating components that are specified by their interface behavior.