Introduction to the SoSyM theme issue on models and evolution

Software artifacts are subject tomany sources of evolutionary pressure, which range from technical changes due to rapidly evolving technology platforms, to modifications caused by new requirements and insights emerging from the business domain. These modifications include changes at all levels, from requirements through architecture and design, to source code, documentation and test suites, and might affect any kinds of models. Therefore, adopting models, techniques, and tools for coping with and managing changes that accompany the evolution of software models is an essential discipline of Software Engineering.