The RelativeValueType is a subtype of the BaseDataVariableType. It is used to inform how values, which are represented by this type, behave, or reference to another value representation.
It is formally defined in Table 17.
Table 17 – RelativeValueType Definition
|
Attribute |
Value |
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|
BrowseName |
RelativeValueType |
|||||
|
IsAbstract |
True |
|||||
|
ValueRank |
-2 (Any) |
|||||
|
DataType |
BaseDataType |
|||||
|
References |
NodeClass |
BrowseName |
DataType |
TypeDefinition |
Other |
|
|
Subtype of the BaseDataVariableType defined in OPC 10000-5 |
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|
0:HasComponent |
Variable |
Base |
0:NodeId |
0:BaseDataVariableType |
O |
|
The Variable Base provides the NodeId of the object on which the Value of this object is based on. The NodeId can be NULL if this Value does not relate to another value.
To express if the Value is constant and does not change, the Constant bit of the Attribute AccessLevelEx of the RelativeValueType Variable shall be set to True.
To express if the base (on which the value is based) is constant, the Constant bit of the Attribute AccessLevelEx of the Variable Base shall be set to True.
Figure 6 shows an example usage to the RelativeValueType and the Variable Base.
