In this paper, we describe a framework for the computer-aided evolution of the designs of object-oriented software systems. Evolution mechanisms are software structures that prepare software for certain type of evolutions. The framework uses a database which holds the evolution mechanisms, modeled as template graph transformations, with the supported evolution types. To evolve the software, the designer enters the type of evolution and provides the names of the software entities that are going to be evolved. The framework fetches the evolution mechanisms, converts the design to a graph model and applies the transformations. As an application of the framework, we implemented a tool for computer-aided evolution that uses object-oriented evolution mechanisms.