5
You can see an association between the classes customer and usage right . This
association is a structure relationship, which means that the structure of the class
customer includes not only the attributes listed in the class symbol, but also a
property, right , of type usage right . 6 The multiplicity states how many values are
included. In this case, it ??™ s one at most.
In contrast, the class usage right has a property, booker , of type customer .
From a pragmatic perspective, there is not much of a difference between attribute
and association. For example, the customer attribute routes can also be represented
as an association to the class route . Looking at the details, however, there
are differences between association and attribute. Rather than discussing them
here I refer to further UML literature; see [61], and [41]. In SysML these differences
refl ect in values, references, and parts.
An association can have a name. If we use a name we write it centered at the
association line. The name of an association often refers to a reading direction,
which is stated by a black triangle in front of the name.
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