What's the difference between process models and approaches. In Ian Sommerville's Software Engineering book, Software processes categorized in to Plan-Driven and Agile. Then he talks about 3 models, Waterfall, Incremental and Reuse-oriented. Then he talk about Rational unified process and then it comes a topic about Boehm spiral model. Is this Boehm spiral model a another type of software process model as Waterfall, Incremental and Reuse-oriented?
Then in Agile software development, he's talking about RAD (Rapid Application Development) is this also a process model? Can we categorize software process models in to the 2 processes (i.e Plan driven and agile)?