The Historical Access model defines additional Propertiesthat are applicable for both HistoricalDataNodes and HistoricalEventNodes.

The DataVariableor Objectthat has Annotationdata will add the Annotations Propertyas shown in Table 2.

Table 2– Annotations Property

Name

Use

Data Type

Description

Standard Properties

Annotations

O

Annotation

The Annotations Propertyis used to indicate that the history collection exposed by a HistoricalDataNode supports Annotationdata. Annotation DataTypeis defined in Subclause 5.5.

Since it is not allowed for Propertiesto have Properties, the Annotations Propertyis only available for DataVariablesor Objects.

The Annotations Propertyshall be present on every HistoricalDataNode that supports modifications, deletions, or additions ofAnnotationsweather or not Annotationscurrently exist. Annotationdata is accessed using the standard HistoryReadfunctions. Annotationsare modified, inserted or deleted using the standard HistoryUpdatefunctions and the UpdateStructuredDataDetailsstructure. The presence of the Annotations Propertydoes not indicate the presence of Annotations on the HistoricalDataNode.

A Servershall add the Annotations Propertyto a HistoricalDataNode only ifit will also support Annotationson that HistoricalDataNode. See OPC 10000-4for adding Properties to Nodes. A Servershall remove all Annotationdata if it removes theAnnotations Propertyfrom an existing HistoricalDataNode.

As with all HistoricalNodes, modifications, deletions or additions of Annotationswill raise the appropriate Historical Audit Event with the corresponding NodeId.