The NotificationMessagestructure used in the Subscription Serviceset allows specifying different types of NotificationData. The NotificationDataparameter is an extensible parameter whose structure depends on the type of Notificationbeing sent. This parameter is defined in Table 164. Other types can be defined by additional parts of OPC 10000 or other specifications based on OPC UA. The ExtensibleParametertype is defined in 7.17.

There may be multiple notifications for a single MonitoredItemin a single NotificationData structure. When that happens the Servershall ensure the notifications appear in the same order that they were queued in the MonitoredItem. These notifications do not need to appear as a contiguous block.

Table 164– NotificationData parameterTypeIds

Symbolic Id	Description
DataChange	Notificationdata parameter used for data change Notifications.
Event	Notificationdata parameter used for Event Notifications.
StatusChange	Notificationdata parameter used for Subscriptionstatus change Notifications.