we propose a repository to characterize OO evolution problematic. The two main objectives are to characterize object evolution according to its own features, and to uniformly analyze and compare evolution strategies according to this proposed repository. For that, OO evolution is defined according to its three fundamental features that we call facets: the subject of evolution (the structure or the behavior of objects), the type of evolution (whether it is foreseeable or not) and the mechanism used to deal with object evolution (from class or instance toward classes or instances). We restrict and develop our study to the structure of an object. We propose a taxonomy on object structure (the node and the arc) and a taxonomy on evolution operations. We distinguish unary and binary operations that apply on the above defined concepts. We then analyze and position some evolution strategies according within this repository and according to those two taxonomies. 1 The three facets of Object Evolution The three facets that we consider as the fundamental features of OO evolution are the subject, the type and the mechanism of evolution: