The Historical Event model defines additional Properties. These descriptions also include required use cases for HistoricalEventNodes.

Historical Access of Events uses an EventFilter. It is important to understand the differences between applying an EventFilter to current Event Notifications, and historical Event retrieval.

In real time monitoring Events are received via Notifications when subscribing to an EventNotifier. The EventFilter provides the filtering and content selection of Event Subscriptions. If an Event Notification conforms to the filter defined by the where parameter of the EventFilter, then the Notification is sent to the Client.

In historical Event retrieval the EventFilter represents the filtering and content selection used to describe what parameters of Events are available in history. These may or may not include all of the parameters of the real-time Event, i.e. not all fields available when the Event was generated may have been stored in history.

The HistoricalEventFilter may change over time so a Client may specify any field for any EventType in the EventFilter. If a field is not stored in the historical collection then the field is set to null when it is referenced in the selectClause or the whereClause.