The development of a complex software system needs a well-planned process to ensure its quality. There are already many existing process models, such as the waterfall model [32], the spiral model [106], the formal methods-based transformation model, and the prototyping model [84], and each model indicates the necessary activities, resources, relations between activities and resources, and necessary technologies for carrying out the activities. Although each of these models has a different emphasis on the way systems are developed, they all share the commonality of using the waterfall model as the underlying concept.