7.1 RelativeValueType
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.
| Attribute | Value | |||||
| BrowseName | RelativeValueType | |||||
| IsAbstract | True | |||||
| ValueRank | -2 (Any) | |||||
| DataType | BaseDataType | |||||
| References | NodeClass | BrowseName | DataType | TypeDefinition | Other | |
|---|---|---|---|---|---|---|
| Subtype of the BaseDataVariableType defined in OPC 10000-5 | ||||||
| 0:HasComponent | Variable | Base | 0:NodeId | 0:BaseDataVariableType | O | |
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.
