Information Technology Reference
In-Depth Information
Requirement
analysis - V & V
Design -V & V
Development
V & V
Testing - V & V
Change
request
V & V = Verification and Validation
Deployment
V & V
Waterfall model with feedback
Figure 7.2
The waterfall model evolves.
by itself does not help in avoiding, until late in the process, the discovery
of defects that may take the project back many phases, and thereby force
rework.
Iterative, Incremental
Most modern software development life cycles stress iteration throughout
the process and add incremental functionality (Figure 7.3) within each
iteration.
Spiral
In response to the deficiencies in the waterfall SDLC, Boehm defined this
iterative life cycle — “spiral model” — of software development in 1988.
This is the basis for most modern software development processes since then.
In the spiral model (Figure 7.4), the cycle starts with certain require-
ments. Projects risks, with respect to the requirements, are evaluated, and
the implementation (development) of the product for that iteration begins.
Once it is complete, customer feedback is obtained, and the next iteration
is initiated. In this iteration, again, the highest risk items are addressed
first. While the parts of this loop may change, the pattern of repetition
and incremental delivery of product are repeated throughout the life cycle.
