Non-functional requirements can describe qualitative aspects of use cases, e.g.,
agreed system response times during a fl ow. This type of relation is modeled by
means of a trace relationship ( Figure 2.39 ).
So far we have been concentrating more on the identifi cation of use cases
and less on the allocation of actors. We ??™ ll catch up on this right now. You can fi nd
2.4 Modeling Use Cases
FIGURE 2-38
Refi ning use cases, requirements.
req [package] Functional requirements [car usage without staff]
?«requirement?»
Car usage
without staff
Start car usage End car usage
?«refine?» ?«refine?»
FIGURE 2-39
Relationship between a use case and a requirement.
uc [package] Car usage [non-functional requirements]
?«interfaceRequirement?»
Reservation system
?«performanceRequirement?»
Period unlock door
?«trace?» ?«trace?»
Start car usage
74 CHAPTER 2 The Pragmatic SYSMOD Approach
examples like the one shown in Figure 2.40 ??”an actor denoted as a stick man,
connected with a use case, in the UML literature.
However, use case diagrams for embedded systems look totally different.
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