This activity describes a top-down approach of logically decomposing the system across multiple aspects driven by
the chosen architectural viewpoints and views (see the Use
Case Flowdown and Supplementary Requirements Flowdown concepts).
Although in most of the cases the starting point will be the top-level use cases, this is not a pre-requisite. If the
use-case techniques are not employed by the modeling team, this operation-based approach could still be used as long as
you can define the operations for the top-level system. This is also true when this activity is performed
for a subsystem for which only the operations have been defined.
There are two other main characteristics of this approach. One, this is a play around two perspectives on the
(sub)systems: black box and white box. You start with the black box perspective and define the externally
visible properties of the system(s), mostly in terms of operations. Then you open up the black box, define or
identify its elements and describe how each system operation is realized by the elements' operations. The second
characteristic of this approach is the fact that is recursive. You are applying the same general method at lower, more
detailed levels, for finer-grained subsystems.
A simplified workflow through this activity is presented below:
|