This issue contains a collection of essays dedicated to Prof. Dr. Martin Gogolla on his 65th birthday. The articles aim to acknowledge Martin’s substantial contributions to software technology throughout his career, starting with his Ph.D. (if not already his Master thesis) through to the present day. Martin’s efforts have helped modeling languages such as OCL and UML become more rigorous and precise, and have made the USE modelling tool a significant and well-known research vehicle.