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Software Process & Team Software Process
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Personal
Software Process & Team Software Process
The
Personal Software Process (PSP) is an SEI technology
that brings discipline to the practices of individual software engineers,
dramatically improving product quality, increasing cost and schedule
predictability, and reducing development cycle time for software.
The
Team Software Process (TSP) is a complementary SEI
technology that enables teams to develop software-intensive products more
effectively. TSP shows a team of engineers how to produce quality
products for planned costs and on aggressive schedules.
Watts
Humphrey developed PSP and TSP at the SEI in the
mid-1990’s. (Watts Humphrey is widely recognized as being the originator of
the CMM
concept.) The
PSP project was aimed at demonstrating that a CMM
level 5 process could be used by an individual to develop high quality software
without excessive process overhead. PSP proved quite successful and
TSP was developed to provide a framework for applying PSP
in a team setting to develop high quality software. The two processes are
licensed SEI technologies. They are
almost always used together in a project setting.
PSP
is a lightweight CMM level 5 process designed for cost effective
individual use. It applies to most structured software development tasks
including requirements definition, architecture design, module development, and
documentation production. It is
capable of efficiently producing very high quality software products. There is
no cost overhead involved in achieving these high software quality levels. In
fact PSP projects are generally faster and cheaper than more
conventional approaches to software development.
TSP
adds a project management layer to the PSP. It helps engineers to
produce quality products for planned costs and on aggressive schedules. It
addresses the CMM level 2 & 3 management processes using high
performance inter-disciplinary work teams. Engineers manage their own work and
take ownership of their plans and processes. TSP helps the
engineers to build a gelled, self-directed team and to perform as effective team
members. It shows management how to guide and support these teams and how to
maintain an environment that fosters high team performance.
TSP
uses team based planning sessions called launches to put detailed project plans
in place. Team based planning has a number of advantages. Five people working
for 4 days will generate a far higher fidelity plan than one person working
alone for 20 days. They will identify more tasks and more dependencies than a
single person, and will be less likely to have a consistent estimating bias.
Errors from multiple uncorrelated estimates tend to cancel out. The team will
develop a plan faster than a single person. They will own it.
They will use it.
The
TSP planning horizon is intentionally short. The initial launch
puts a top-level plan in place for the entire project and a detailed plan
covering the next three months. Re-launches
are performed every three months to create the detailed plan for the next
quarter or whenever circumstances change so much that the existing plan is no
longer applicable. The short
planning horizon avoids the problem of creating needlessly detailed plans for
things that are likely to change anyway while encouraging the production of a
high-fidelity detailed plan covering the next cycle. The high level of detail
makes it much easier to get accurate estimates and facilitates accurate progress
tracking. Adjustments to the plan can occur at any time. The launches are not
training; they are part of the project.
A
weekly status meeting provides the mechanism for tracking and reporting
progress. Each team member tracks
and presents his or her own status for the week. The process is designed so that
peer pressure becomes a powerful force motivating performance.
PSP
augmented by TSP can support the development of large-scale
software systems. It can be used to accelerate an organization from CMM level
2 to level 5. It provides an excellent foundation for application of six sigma
statistical tools. It does not require a high level of process maturity for
introduction. CMM Level 1
organizations have used it very successfully.
TSP
has been used with pure software teams and with mixed teams of hardware,
software, systems, and test professionals.
It has been shown to sharply reduce total development cost. In our
experience, it has been common for new TSP teams to increase
productivity from 30%-50% within one year. Product quality, measured in terms of
defect escapes, typically improves 4x in the first year and gradually moves to
10x improvement.
PSP
and TSP are applicable to new development and maintenance. Team
size ranges from 5 - 15 professionals for simple teams. Larger multi-teams can
range up to several dozen professionals.
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