The GuardVariableType provides the information of a Guard of a Transition in a StateMachine. A Guard indicates, if the Transition can be used or not. The Guard defines a semantic that can be evaluated to "True" or "False". Only if the semantic is "True", the Transition connected via a HasGuard Reference can be used. The value of the GuardVariableType provides the semantic of the Guard in a human-readable way, that can be used to display the StateMachine.
This base GuardVariableType does not define a machine-readable semantic of the Guard. The calculation, if the Guard is "True" or "False" is server-specific. Subtypes of this VariableType do define concrete machine-readable semantics.
The GuardVariableType is formally defined in Table 20.
Table 20 – GuardVariableType definition
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Attribute |
Value |
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BrowseName |
GuardVariableType |
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DataType |
LocalizedText |
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ValueRank |
−1 (−1 = Scalar) |
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IsAbstract |
False |
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References |
NodeClass |
BrowseName |
DataType |
TypeDefinition |
ModellingRule |
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Subtype of the BaseDataVariableType defined in Clause OPC 10000-5. Note that a Reference to this subtype is not shown in the definition of the BaseDataVariableType. |
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HasSubtype |
VariableType |
ElseGuardVariableType |
Defined in Clause 4.6.6 |
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HasSubtype |
VariableType |
ExpressionGuardVariableType |
Defined in Clause 4.6.5 |
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Conformance Units |
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Base Info Choice States |
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