Over the years, a variety of software process models have been designed to structure, describe and prescribe the software systems construction process. More recently, software process modelling is increasingly dealing with new challenges raised by the tests that the software industry has to face. This book addresses these new trends in software process modeling related to: 1. Processes for open source software; 2. Systems dynamics to model and simulate the software process; 3. Peopleware: the importance of people in the software development and by extension in the software process. One new software development trend is the development of open source projects. As such projects are a recent creation, the process model governing this type of developments is unfamiliar. This book deals with process modeling for open source software. It also deals with software process simulation applied to the management of software projects and improves the software development process capability accor