A task set is a collection of software engineering work tasks, milestones, and deliverables that must be accomplished to complete a particular project. The task set to be chosen must provide enough discipline to achieve high software quality. But, at the same time, it must not burden the project team with unnecessary work.

Task sets are designed to accommodate different types of projects and different degrees of rigor. Although it is difficult to develop a comprehensive taxonomy of software project types, most software organizations encounter the following projects:

1. Concept development projects that are initiated to explore some new business concept or application of some new technology.

2. New application development projects that are undertaken as a consequence of a specific customer request.

3. Application enhancement projects that occur when existing software undergoes major modifications to function, performance, or interfaces that are observable by the end-user.

4. Application maintenance projects that correct, adapt, or extend existing software in ways that may not be immediately obvious to the end-user.

5. Reengineering projects that are undertaken with the intent of rebuilding an existing (legacy) system in whole or in part.

Even within a single project type, many factors influence the task set to be chosen. When taken in combination, these factors provide an indication of the degree of rigor with which the software process should be applied.