Stepwise+refinement

More commonly known as "Top-down and bottom-up design".

Top-down and bottom-up design are stratagies of information processing and knowledge editing. The Top-down approach (known as step-wise design) is essentially the breaking down of a systyem to gain insight into its compositional sub-systems. In a top-down approach an overview of the system is formulated, sepcifying but not detailing any first-level subsystems. Each subsystem is then refine in yet greater detail, sometimes in many additional subsystem levels, until the entire specification is reduce to the basics. A Bottom-up approach is the piecing together of systems to give rise to grander systems, therefore making the original systems sub-systems of the emergent system. In a bottom-up approach the individual base elements of the system are first specified in great detail. These elements are then linked together to form larger subsystems, which then in turn are linked, sometimes in many levels, until a complete top-level system is formed.