What is a Complex Component?

A component is a non-trivial, nearly independent, and replaceable part of a system that fulfills a clear function ... [It] can be used in assembling a well-defined architecture [or application] ... A component conforms to and provides the physical realisation of a set of interfaces that specify some logical abstraction (i.e. System Behaviour)’

Booch, Grady

‘Reusable software components are self-contained, clearly identifiable pieces that describe and/or perform specific functions, have clear interfaces, appropriate documentation, and a defined reuse status’

Sametinger, Johannes

As component it is understood all functionality used in a system. Depending on the degree of abstraction, the components are divided into two large groups: simple and complex components. A simple component gives answer to one functionality at the lowest degree of abstraction, whilst a complex component is made up of the harmonic assembly of several simple and/or complex components.

The following diagram shows simple components as ellipses, and complex components as rectangles. A simple component would be for instance the request for user/password to gain the level access a user can have on a system. A complex component would be the access control to a system, or the management of the access control to a system; this last one would be made up of, at least, the access control and users management.