The extended requirement adds the following
properties:
?– Priority : How important is this requirement? This piece of information helps
you focus on high-priority requirements.
?– Obligation : Is the requirement obligatory or just desirable?
?– Stability : Will the requirement change in the course of the system ??™ s development,
or will it remain stable?
?– Type : The user type includes requirements specifi ed by the contractor.
The system type normally includes requirements that emerge from refi ning
contractor requirements and by including a technical solution. Requirement
types refl ect the difference between user specifi cation and system
specifi cation.
ibd [block] On-board computer context [fastening a card reader]
:Card reader
?«mechanical block?»
:Suction cup
2
?«mechanical block?»
:Case
?«mechanical connector?»
:Windshield
?«mechanical connector?»
FIGURE 5-4
Modeling mechanical elements.
5.3 Extended Requirement
Defi nition
An extended requirement is a requirement that extends the requirement in
question by the following properties: priority , obligation , stability , type , and risks .
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