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Chapter 7. MDSD and SysML 173
The conceptual stage precedes the detailed elaboration of the components
within the different engineering disciplines. Therefore, the conceptual design
plays many central roles in the product life cycle, Next, we emphasize some of
the most important ones, in our opinion.
The formal description of the product at an early stage of the life cycle
improves the understanding of the product requirements and how they
answer the customer needs. The allocation of requirements to the model
elements ensures that these needs are covered and provides a rationale for
the engineer in charge of fulfilling these requirements. The rationalization of
the design is therefore a communication tool spanning organizational levels
and life cycle stages. It improves communication across teams, between
teams (think of the different engineering disciplines) and between teams and
decision makers. It uses a generic language (in the sense that it is not specific
to any engineering discipline) that accommodates the incremental detailing of
the product representation. That last aspect allows coping with organizational
levels. Note that such a formal description is well suited to methodologies.
The SysML model provides an electronic representation of the product that is
leveraged as a decision tool. Trade-off studies are performed by evaluating
functions on the model (cost function, estimation of the integration effort). At
an early stage in the life cycle, often rough estimations are used, hence the
model need not necessarily have a great amount of detail in order to be used
efficiently. When details are added, or artifacts (for example, sub-system
simulations) are produced by detailed engineering, the model is used to
orchestrate the various simulations and perform requirement verification.
Hence the SysML model is an evolving decision tool available throughout the
whole life cycle of the product, and not only at the conceptual stage.
The product model represents abstractions of artifacts that are progressively
elaborated throughout the life cycle. These artifacts are distributed across the
engineering disciplines participating to the design. Hence the model forms a
traceability scaffold that provides a means to measure the development
progress, perform change impact analysis, and manage dependencies
between processes and the produced artifacts. The SysML model is therefore
a management and integration tool for the stakeholders.