The AllowedSubtype is a concrete ReferenceType and can be used directly. It is a subtype of HierarchicalReferences.

The semantic of this ReferenceType is to link from a SubtypeRestriction Object to a Variable defining one allowed subtype.

The SourceNode of References of this type shall be an Object of SubtypeRestrictionType (see OPC 10000-5) or a subtype.

The TargetNode of this ReferenceType shall be a Variable of BaseDataVariableType or a subtype. The DataType, ValueRank and ArrayDimensions of the Variable shall follow the rules defined in 5.8.6.

It is recommended that the BrowseName of the Variable describes the used DataType including its ValueRank. However, it should not use the NamespaceIndex of the DataType NodeId unless it is defined in the same Namespace.

It is not allowed to reference two Variables with the same BrowseName using the AllowedSubtype ReferenceType or a subtype from the same SourceNode.