Figure 2 illustrate the references defined by this specification (outlined in red). Each reference type is describe in there own sections.

Figure 2 – ReferenceType hierarchy

This ReferenceType is a concrete ReferenceType that can be used directly. It is a subtype of the Aggregates ReferenceType and will be used to refer from a Historical Node to one or more HistoricalDataConfigurationType Objects or HistoricalEventConfigurationType Objects.

The semantic indicates that the target Node is “used” by the source Node of the Reference. Its representation in the AddressSpace is specified in Table 7.

Table 7 – HasHistoricalConfiguration ReferenceType

Attributes	Value
BrowseName	HasHistoricalConfiguration
InverseName	HistoricalConfigurationOf
Symmetric	False
IsAbstract	False
References	NodeClass	BrowseName	Comment
The subtype of Aggregates ReferenceType is defined in OPC 10000-5.
ConformanceUnits
Historical Access Read Raw
Historical Access Time Instance
Historical Access Aggregates
Historical Access Events

This ReferenceType is a concrete ReferenceType that can be used directly. It is a subtype of the NonHierarchicalReferences ReferenceType and will be used to refer from a HistoricalDataNode to a Node that is the source of the data being historized by the Source Node. Typically, this node is an external node in another Server.

Its representation in the AddressSpace is specified in Table 8. The Source node of this reference type shall be a HistoricalDataNode. The Target node shall be any Variable or Property

Table 8 – HasCurrentData ReferenceType

Attributes	Value
BrowseName	HasCurrentData
InverseName	HasHistoricalData
Symmetric	False
IsAbstract	False
References	NodeClass	BrowseName	Comment
The subtype of NonHierarchicalReferences ReferenceType is defined in OPC 10000-5.
ConformanceUnits
Historical Access HasCurrentData

This ReferenceType is a concrete ReferenceType that can be used directly. It is a subtype of the NonHierarchicalReferences ReferenceType and will be used to relate HistoricalEventNode to a Node that is the source of the data being historized. Typically, this node is an external node in another Server.

Its representation in the AddressSpace is specified in Table 9. The Source node of this reference type shall be a HistoricalEventNode. The Target node shall be any Object or View that has the EventNotifier Attribute set to TRUE.

Table 9 – HasCurrentEvent ReferenceType

Attributes	Value
BrowseName	HasCurrentEvent
InverseName	HasHistoricalEvent
Symmetric	False
IsAbstract	False
References	NodeClass	BrowseName	Comment
The subtype of NonHierarchicalReferences ReferenceType is defined in OPC 10000-5.
ConformanceUnits
Historical Access HasCurrentEvent