It is traditional to look to any engineering activity from both the product point of view and the process point of view. The product is the desired result, the process is the route followed to reach the result. Methods were classically focused on the product aspect of systems development and have paid less attention to the description of formally defined ways-of-working. Clearly, there is an important demand on methods and tools where process guidance is offered to provide advice on which activities are appropriate to which situations and how to perform them [Rolland95], [Rolland96], [Downson94], [Wynekoop93]. We propose a way-of-working which intents to provide such a guidance.