Wave Process Model (WPM) is a new descriptive model representation of a software development process. The idea of this representative description is elaborated with a case study of an open source software development. According to any kinds of software developments, which mostly have a characteristics of repeated works done are described in this book to have a kind of phases which can be spitted in to different wave of doings. Based on this WPM kinds of modelling in case of open source software development, it is assumed to motivate a future work of applying this process model for other kinds of software developments and project managements.