Waterfall model
The waterfall model is a classical
life cycle approach of software development
(SEM V 3.0 is implicitly based on this model). Each phase
contains constructive and checking activities (e.g.
producing and subsequent reviewing of a software
requirements specification in the Definition phase). In
principle, all phases are executed sequentially in this
model. Only if the results of one phase are available can
the next phase be started.Other models
supported by stdSEM:
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The evolutionary
development model is used in PSE
to execute all maintenance projects and the major
version developments. Each follow-up product
version is based on the preceding version. The
specifications, plans and implementations
produced in follow-up versions cover only those
features that distinguish the new version from
the old one. |
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While the prototyping
model is based on a software
requirements specification (important for
contractual purposes!), the design and
implementation are executed using appropriate
development tools. Product development can take
place in close cooperation with the customer
using the resulting prototype (described in
stdSEM as a separate Prototyping
"phase" in parallel to the traditional
Design and Implementation phases). |
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In the case of the incremental
delivery model, development is
based on a uniform software requirements
specification and architectural design
specification. The required overall solution is
then subdivided into a series of independent
subprojects, however (e.g. for deadline reasons,
to complete important product parts as early as
possible, or to provide support to development
teams working in parallel). Each of the
subprojects then results in an operational
product version. |
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The SEM spiral
model is essentially a waterfall
model with comprehensive accompanying measures
which is useful for very large projects (new goal
definition, risk analysis, simulation, etc.,
after each phase cycle). This model therefore
tends to be used rarely in PSE. |
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