Software Evolution based on Formalized Abstraction Hierarchy

Software evolution is about visions and abstractions. The success in finding the right visions, i.e., directions of future evolution, and abstractions, i.e., concepts by which the system is understood, provide a good starting point for the evolution of a software system. In contrast, a failure makes the system practically unevolvable. Unfortunately, there is no universally accepted set of visions or abstractions that could be applied in all systems. Instead, it is up to the developers to find and document them in particular domains. Then, criteria are needed for determining the quality of interconnected abstractions and visions. This can be achieved by modeling the abstractions incorporated in the system as a hierarchy, where abstraction levels exceeding that of implementation facilities are used. The hierarchy can then be used for examining new visions and requirements that emerge over time as well as for supporting associated modifications. This paper introduces an approach where formalism is used for deriving the hierarchy, and provides an example on the evolution of abstractions.