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29 .
4.5.3 Value Type
Defi nition
A value type defines values that have no identity, and cannot be referenced by
a block, but can have a unit or dimension.
It is a stereotype ?«valueType?» of the UML element data type.
UML data types describe values that have no identity, for example, integers. This
means that two data types with the same value cannot be distinguished. This is
different with instances of blocks or UML classes. They can be distinguished, even
if they have the same attribute values.
A value type is a data type with the added property that it can have a unit and
dimension. This means that you can defi ne a unit as a type ( Figure 4.35 ).
248 CHAPTER 4 SysML??”The Systems Modeling Language
The notation is identical to that for the UML data type, except that we write
the stereotype ?«valueType?» above the name. The stereotype name also serves as
heading of the compartment for which the unit or dimension is described ( Figure
4.35 ).
4.5.4 Unit and Dimension
FIGURE 4-35
Value types.
FIGURE 4-34
SysML distribution defi nitions.


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