Precision of description of subsystem components

It is not easy to describe what a subroutine does. What in one frame of mind must be described externally as a side effect may be considered in another frame as merely an internal matter for the routine implementation.

The object style of sub-system description encourages the sub-system implementer to provide all necessary function and thereby avoid the necessity of the client delving into internals. Our experience is that defining and implementing a complete interface to an object is an effective use of the designer's and implementer's time.

The system architecture makes circumvention of object integrity very difficult and thus encourages the style of design that we consider good.

When sub-system function description is achieved as claimed here, a complex system can be more effectively decomposed into simpler components with less danger of mis-understanding of responsibilities. This, in turn, supports parallel implementation stratagies and leads to system design that is more comprehensible to those that will fix and enhance the system.