Clements Szyperski approaches the definition of a component in his book on component based software-engineering with the statement "Components are for composition, much beyond is unclear" []. This statement does not only point out how hard it is to find a common definition for the term "component". It also highlights the most common principle in the definitions of the term component in the literature: a component can be composed with other components in order to get a more complex structure. We also consider the ability to compose components into new structures as a primary feature of components. As a consequence, our component model contains an abstract conceptual view of the concept of a "composite structure", which is a structure build by composing components.