???2
We use the term preliminary analysis for this preparatory activity where we
select the subset of features to include, identify the state and the actions that we will
represent, and choose the level of abstraction.
Writing a model program can be a useful activity in its own right. When we (the
authors) write a model program, we usually find that the source materials provided
to us ??“ the informal specifications and design documents ??“ are ambiguous and incomplete.
We can always come up with a list of questions for the architects
and designers. In the course of resolving these, the source materials are revised.
Clarifications are made; future misunderstandings with developers and customers
are avoided. Potential problems and outright errors are often exposed and corrected.
1.2 Model-based analysis
Model-based analysis uses a model program to debug and improve specifications and
designs, including architectural descriptions and protocols. Model-based analysis
can also help to validate the model programs themselves: to show that they actually
2 The quotation is from Jackson and Damon (1996).
6 Describe, Analyze, Test
do behave as intended. The model program is expressed in a formal notation (a
programming language), so it can be analyzed automatically. Analysis uses the
same model programs and much of the same technology as testing.
Runs of the model program are simulations (or animations) that can expose
problems by revealing unintended or unexpected behaviors.
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