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Does the information fl ow trigger a new use case fl ow, or is it part
of another fl ow? In case of doubt, we assume for now that a new fl ow is triggered.
FIGURE 2-31
The approach model for use cases.
act Model use cases
Model object
flow
Use cases
[detailed]
Requirements
Use cases
[object flow]
Describe use cases
essences
Use cases
[essential]
Use cases
Requirements
Model use cases without
redundancies
Use cases
[non-redundant]
Use cases
Describe system
processes
Use cases
Identify use
cases
Use cases
System context
Model use
case flows
Use cases
[detailed]
Requirements
Use cases
[essential]
Requirements
Requirements
System context
Use cases System
processes
System processes
67
Each newly found fl ow is a use case for our system. The categories we have
grouped our actors in are helpful in this step.
When the actor ??™ s end, where the information fl ow starts, is a user we have to
ask ourselves what the user wants of our system. The information fl ow is part of a
dialog between a user and the system.


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