The Attributes of Objects or Views that have importance for historical Events are specified in detail in OPC 10000-3. The following Attributes are particularly important for a HistoricalEventNode:

• EventNotifier OptionSet bits:
• HistoryRead 2 Indicates if the history of the Events is readable. (0 means not readable, 1 means readable).
• HistoryWrite 3 Indicates if the history of the Events is writable. (0 means not writable, 1 means writable).

The EventNotifier Attribute is used to indicate if the Node can be used to read and/or update historical Events.