This paper presents a model for software architecture evolution, called SAEV (Software Architecture EVolution Model). A software architecture is defined through its architectural elements (components, connectors, configurations...). We associate to these architectural elements three abstraction levels namely from the most abstract one: the meta level, the architectural level and the application one. SAEV offers a whole of concepts, which are evolution operations, evolution rules, evolution strategies and invariants, to describe and manage uniformly the evolution of architectures at the architectural level as well as at the application level. This is done independently of any description or implementation language. In addition, SAEV offers a uniform mechanism to carry out a given evolution at these different levels.