Abstract
We propose a formal model with mathematical definitions to represent and explore the complicated hierarchy and multidimensional structure of software evolution. This formalization of software evolution is based on a hyper-graph and extended to an evolutionary hyper-graph with different software evolution objects. In an evolutionary hyper-graph, a top-level software evolution step can be refined into several finer software evolution steps and related top-level software evolution components can be decomposed into finer software evolution components. The hyper-graph model in conjunction with prototyping can help developers describe and understand soft-ware evolution processes. We provide an example of multimedia system evolution to illustrate this formalization.