Very general requirements that
have rather the status of a heading contain more specific, more detailed requirements.
A namespace containment shows this relation. It is subject to the rule that
the master requirement is satisfied when all of its sub-requirements are satisfied.
Formally the relationship means that a requirement is present in the
namespace of the master requirement. The consequence is that a requirement
must not contain requirements by the same name, which makes sense. Another
consequence is that a requirement must not concurrently be part of more than
one requirement. 1 This latter rule contradicts the need to reuse requirements in
other contexts. SysML offers the copy relationship to this end.
req [package] Usability requirements [select alternative notation]
?«businessRequirement?»
Usage comfort
?«performanceRequirement?»
Response time
reservation system
Derived
?«requirement?» Response time
reservation system
DerivedFrom
?«requirement?» Usage comfort
231
The namespace containment corresponds to the UML notation for the representation
of nested classes (think of ??? inner class ??? ): a circle with a cross, from
which starts a line to the contained element ( Figure 4.
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