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Two equal values cannot
be distinguished. This is different with classes. Two objects with the same
attribute values can be distinguished: they are equal but not identical.
Data types are denoted like classes, with the keyword ?«dataType?» above the
name ( Figure 3.22 ).
A primitive type has no structures. For example, date is not a primitive type
since it has structure elements like day , month , and year . UML has four predefi -
ned primitive types: Integer , Boolean , String , and UnlimitedNatural. Unlimited
Natural is the value range for natural numbers, including zero and * as the symbol
for infi nite.
163
A primitive type is denoted like a class, with the keyword ?«primitive?» above
the name ( Figure 3.22 ).
Another special data type is enumeration. Its value range consists of a limited
set of literals, which have to be fully stated. Figure 3.22 shows an example of an
extended control value with four literals.
3.3.12 Association Class
class Pumping system
Container
0..2 0..1
Pump
Hose
diameter:Integer
FIGURE 3-23
Example for an association class.


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