Modeling reality -- vernacular
- requirements -- use cases
- analysis -- domain concepts
- design -- system architecture
- implementation -- language support
Design model -- system oriented
- provides a justification of the architecture
slide: Perspectives of modeling
An important contribution of [Jacobs92]
is the notion of use cases
that describe the situations in which a user actually
interacts with the system.
Such a (use case) model is an important constituent of
the requirements document, since it precisely
describes what the system is intended for.
For the purpose of analysis,
it may be helpful
to develop a more encompassing (conceptual) model
of the problem domain.
The advantage of such an approach is that the actual system
may later easily be extended due to the generality
of the underlying analysis model.
In contrast to the model used in analysis,
both the design model and the implementation model are more
solution oriented than domain oriented.
The implementation model is clearly dependent on the available
language support.
Within a traditional life-cycle, the design model may be seen as
a transition from analysis to implementation.
The notion of objects may act as a unifying factor,
relating the concepts described in the analysis document
to the components around which the design model is built.
However, as we have noted, object-oriented development
does not necessarily follow the course
of a traditional software life-cycle.
Alternatively, we may characterize the function of the
design document as a justification of the choices
made in deciding on the final architecture of the system.
This remark holds insofar as an object-oriented approach
is adopted for both design and implementation.
However, see [Hend90] for a variety of combinations of
structured, functional and object-oriented techniques.
Dimensions of modeling
When restricting ourselves to design models,
we may again distinguish between different modeling
perspectives or, which is perhaps more adequate
in this context, dimensions of modeling.
In [Rum91], it is proposed to use three complementary
models for describing the architecture and functionality
of a system.
See slide [3-dimensions].
