Technical systems of today often include large amounts of embedded software. Today, in general, embedded software offers various functionalities, is distributed over networks and structured into logical components that interact. To understand and develop software-intensive systems we need fundamental models of multi-functional software system combining services and composed of concurrently interacting components forming architectures. We need methods to specify system properties, identify and describe various basic views onto systems, and show how they are related.

We consider, in particular, models of data, functionality, states, interfaces, interaction, hierarchical composed systems, and processes. We study relationships by abstraction and refinement as well as forms of composition and modularity. In particular, we introduce a comprehensive mathematical model for composed systems, their views and their relationships as needed in a comprehensive development process. Finally we outline a consequent architecture-centered model driven development process.