| Representation Options |
UML Representation: Model, stereotyped as <<analysis model>>.
The analysis model may have the following properties:
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Introduction: A textual description that serves as a brief introduction to the model.
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Analysis Packages: The packages in the model, representing a hierarchy.
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Classes: The classes in the model, owned by the packages.
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Relationships: The relationships in the model, owned by the packages.
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Use-Case Realizations: The use-case realizations in the model, owned by the packages.
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Diagrams : The diagrams in the model, owned by the packages.
Normally, "analysis classes" will evolve directly into elements in the Design Model: some become design classes, others
become design subsystems. The goal of Analysis is to identify a preliminary mapping of required behavior onto modeling
elements in the system. The goal of Design is to transform this preliminary (and somewhat idealized) mapping into a set
of model elements which can be implemented. As a result, there is a refinement in detail and precision as one moves
from Analysis through Design. As a result, the "analysis classes" are often quite fluid, changeable, and evolve greatly
before they solidify in the Design activities.
Points to consider when deciding whether a separate Analysis Model is needed:
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A separate Analysis Model can be useful when the system must be designed for multiple target environments, with
separate design architectures. The Analysis Model is an abstraction, or a generalization, of the Design Model. It
omits most of the details of the design in order to provide an overview of the system's functionality.
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The design is complex, such that a simplified, abstracted "design" is needed to introduce the design to new team
members. Again, a well-defined architecture can server the same purpose.
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The extra work required to ensure that the Analysis & Design models remain consistent must be balanced against
the benefit of having a view of the system which represents only the most important details of how the system
works. It can be very costly to maintain a high degree of fidelity between the Analysis Model and the Design Model.
A less ambitious approach might be to maintain the Analysis Model with only the most important domain classes and
the key abstractions in the design. As the complexity of the Analysis Model increases, so does the cost to maintain
it.
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Once the Analysis Model is no longer maintained, its value decays rapidly. At some point, if it is not maintained,
it will cease to be useful as it no longer will accurately reflect the current design of the system. Deciding to no
longer maintain the Analysis Model may be appropriate (it may have served its purpose), but the decision should be
a conscious one.
In some companies, where systems live for decades, or where there are many variants of the system, a separate analysis
model has proven useful.
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