A discipline is a collection of tasks that are related to a major "area of concern" within the overall project. Grouping tasks into disciplines is mainly an aid to understanding the project from a traditional waterfall perspective. Although it is more common to perform tasks concurrently across several disciplines (for example, certain requirements tasks are performed in close coordination with analysis and design tasks), separating these tasks into distinct disciplines is simply an effective way to organize content, which makes comprehension easier.

Another reason that several tasks are all categorized by the same discipline is that they represent a part in achieving a higher goal, or performing work tasks that are all related to each other. Every discipline defines standard ways of doing the work it categorizes. Such standard ways are expressed by so-called reference workflows described with capability patterns, which define how the tasks categorized by the discipline work together (in the most generic way). These reference workflows are often used for educating and teaching practitioners.

Like other workflows, a discipline's reference workflow is a semi-ordered sequence of activities, presented as either a breakdown structure or an activity diagram performed to achieve a particular result. The "semi-ordered" nature of discipline workflows emphasizes that the discipline workflows cannot present the real nuances of scheduling real work, for they cannot depict the optionality of activities, or the iterative nature of real projects. Yet they still have value as a way for us to understand the process, by breaking it into smaller areas of concern.