Motivation

Planning an iterative project is both harder and easier than planning a waterfall project:

• It is harder and much more work, since the planning is more dynamic and ongoing.

• It is easier because it is much more in tune with the goals of the project. There is a short- term planning horizon and plenty of opportunities to adjust the plans.

Traditional planning of engineering projects is far too often organized from the top down and around a product breakdown, that is, the decomposition of the system into components and the various artifact products (specifications, blueprints, subassemblies, and so on), a style of planning that was inherited from the manufacturing and construction industries. Although at some point the plan needs to acknowledge the artifacts and the product structure, this is often done too early in the software development, at a point when little is known about the product.

Planning in the RUP is more focused on a process breakdown, that is, what needs to be done to achieve certain objectives over time. This is where you will see in action the concepts of phases and iterations , as well as the major and minor milestones that accompany them. You will use activities and workflow details. Planning in the RUP will use both a top-down approach and a bottom-up approach ”top-down only in the early stages (Inception and Elaboration phases), complemented by bottom-up in later stages (Construction and Transition phases). ^[1] The bottom-up approach will use the defined artifacts and the architectural baseline. In practice, however, the planning approach is not quite that black-and-white, and there is a continuum across the development lifecycle.

^[1] See Royce 1998, Chapter 10.

This dynamic and iterative approach to planning allows you to achieve a better balance between targets (where you want to be at the end of the project) and commitments (what the team needs to do to get there). It is adaptive and driven by risks, as well as by what has been learned so far about both the product and the process used to develop it.