Identifying operations
Here we discuss operation identification by using sequence diagrams.
MDSD Step 7: Operation identification
Operation identification involves the use of a sequence diagram. Sequence diagrams show the same flow of events described in a use case, but use a very specific format and method to show them. The flow of events of each use case is shown as a series of interactions, more specifically requests from one entity to another. The use case is carried out as entities makes requests of one another.
We create two kinds of sequence diagrams in
For each use case, draw a
1.This use case begins when the driver approaches and unlocks the car.
2.The driver starts the car and allows it to warm up.
3.The driver drives the car to the work location.
4.And so forth...
We must transform this plain language flow of events into a series of requests. We do this by asking, for each step or set of steps in the use case, what request is being made of the system do to something. Sometimes this takes a combination of imagination and reading ahead in the use case to determine the actual purpose of things.
In the example here, we might ask what request is being made in the first step. By approaching the car, is the driver making some request of the car? It might be tempting to draw this on a sequence diagram as an arrow from the driver to the system, and label it as approach car but this is not correct (Figure
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