The unified modeling language (UML) has been adopted by the Object Management Group for use in developing object-oriented software systems, and has gained wide acceptance in industry. However UML is a large and complex language, with many features in need of refinement or clarification, and there are different views about how to use UML to build these systems. This book sheds light on such issues, by illustrating how UML can be used successfully in practice as well as identifying various problematic aspects of UML and suggesting possible solutions. As an edited collection of insightful contributions from both industry and academia, this book should appear to researchers, practitioners and instructors of UML.