1.3 DEVELOPMENT PHASING
Development usually progresses through distinct levels or stages:
° Concept level, which produces a system concept description (usually described in a concept study);
° System level, which produces a system description in performance requirement terms; and
° Subsystem/Component level, which produces first a
set of subsystem and component product performance descriptions, then a set
of corresponding detailed descriptions of the products' characteristics,
essential for their production.
The systems engineering process is applied to each level of system development, one level at a time, to produce these descriptions commonly called configuration baselines. This results in a series of configuration baselines, one at each development level. These baselines become more detailed with each level.
In the Department of Defense (DoD) the configuration
baselines are called the functional baseline for the system-level description,
the allocated baseline for the subsystem/component performance descriptions,
and the product baseline for the subsystem/component detail descriptions.
shows the basic relationships between the baselines. The triangles
represent baseline control decision points, and are usually referred to as
technical reviews or audits.
Levels of Development Considerations
Significant development at any given level in the system hierarchy should
not occur until the configuration baselines at the higher levels are
considered complete, stable, and controlled. Reviews and audits are used to
ensure that the baselines are ready for the next level of development. As will
be shown in the next chapter, this review and audit process also provides the
necessary assessment of system maturity, which supports the DoD Milestone