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Chapter 3. Black-box thinking: Defining the system context 65
This is a benefit of an MDSD model—it maps these interaction requirements in
the same model with system functional requirements and usage scenarios,
ensuring consistency.
Having now determined our set of candidate operations, by producing sequence
diagrams for all use cases (including alternate flows), we now move to the next
major step, during which we will produce a consistent, optimal set of operations.
Refactoring operations
Here we consider refactoring and consolidating operations.
MDSD Step 8: Refactoring and consolidating enterprise
operations
It might seem that we have determined all of the operations necessary for an
entity to fulfill all of its use cases, but there is one final step. In most situations, we
find that due to the elapsed time it takes to create a complete use case model,
and the fact that usually multiple modelers are involved, we must ensure that the
operations determined from the analysis of the entire collection of use cases do
not include redundant or overlapping operations.
To do this, review the list of operations that you have identified from analysis of all
the entity’s use cases. Look for any operations that might be similar but named
slightly differently. For example, if in one use case an operation was identified
called start-up and in another initialize we might look more closely into these to
see if they could be treated as the same operation. If so, then rename one or
both of them so they are the same, and make any necessary adjustments to the
use case flows of events and black-box sequence diagrams to make it all
consistent.
In the early stages of an MDSD model, you can expect lots of this kind of
refactoring and rethinking of the model.
More about operations
Now that we have identified the set of operations necessary to fulfill (or
accomplish) the use cases, let us look more closely at what an operation is and
what it represents in an MDSD model. Operations are like use cases, in that they
are flows of events that accomplish something. In addition, they do show
primarily interactions between system elements and actors, while hiding
functionality internal to those elements.