Personal Software Process
It is aligned with and designed for use in organizations that work with CMMI or ISO 15504 process models, although its principles of personal measurement can be applied in any context.
Fundamentals
PSP is based on the premise that software quality ultimately depends on the people who build it. To improve product quality, individual work processes must be improved: how each engineer plans, estimates, designs, codes, and tests.
PSP proposes that each engineer keep a personal record of:
- The time spent on each phase of the work (elapsed time vs. ideal time).
- The defects they introduce and when they detect them (during coding, review, or testing).
- The size of the code they produce.
With this data, engineers can calibrate their own estimates, understand in which phases they introduce the most defects, and improve continuously.
Relationship with Teamwork
The PSP has a version for small teams called TSP (Team Software Process), also developed by Humphrey. While PSP focuses on individual improvement, TSP coordinates teams of 2 to 20 people by applying similar measurement and process principles.
PSP and ideal time
One of PSP's contributions to the vocabulary of agile management is the distinction between ideal time (effective working time, without interruptions) and elapsed time (the full working day). PSP calls this Delta Time. This distinction, adopted by agile project management, is the basis of the ideal-time estimation that technical Scrum uses to plan sprints.
Common mistake
Applying PSP in organizations that lack the necessary measurement culture. PSP requires engineers to keep detailed individual records of their work. Without a culture of psychological safety and continuous improvement, time and defect tracking can be perceived as a surveillance system rather than as a tool for personal improvement, and the data stops being reliable.
References
- Humphrey, Watts S. (1995). A Discipline for Software Engineering. Addison-Wesley.
See also
Want to advance in agility? You can search for course and exam calls or go at your own pace by becoming a member of the Agile Club. This membership includes exclusive resources, e-learning classrooms, and access to Skill Arena: a space to practice and measure your agile skills at your own pace.