Workflows

A mere enumeration of all roles, activities, and artifacts does not quite constitute a process. We need a way to describe meaningful sequences of activities that produce some valuable result and to show interactions between and among roles. A workflow is a sequence of activities that produces a result of observable value. In UML terms, a workflow can be expressed as a sequence diagram, a collaboration diagram, or an activity diagram. We use a form of activity diagrams in this book. Figure 3-6 is an example of a workflow.

Note that it is rarely possible or practical to represent all the dependencies between activities. Often, two activities are more tightly interwoven than shown, especially when they involve the same role or the same individual. People are not machines, and the workflow cannot be interpreted literally as a program that people are to follow exactly and mechanically.

The Rational Unified Process uses three types of workflow:

• Core workflows, associated to each discipline

• Workflow details, to refine the core workflow

• Iteration plans

Core Workflows

In each discipline there is a core workflow that gives the overall flow of activities.

Workflow Details

Each core workflow covers a lot of ground. To break them down, we use workflow details to express a specific group of closely related activities. For example, the activities are performed together or in a cyclical fashion; they are performed by a group of people working together in a workshop; or they produce an interesting intermediate result. Workflow details also show information flows ”the artifacts that are input to and output from the activities ”to show how activities interact through the various artifacts.

Iteration Plans

Iteration plans are another means of presenting the process, describing it more from the perspective of what happens in a typical iteration. They are actually the closest to what a workflow engine would handle. You can look at them as instantiations of the process for one given iteration, selecting the activities that will be effectively run during the iteration and replicating them as necessary. There are an infinite number of ways you can instantiate the process. The Rational Unified Process contains descriptions of a few typical iteration plans. They are given primarily for pedagogical purposes, as you can see with the few examples given in Chapter 16.