Verifying the notification matches your business needs
The events process computes the values of the notification variables when it creates the notification in the sys_email table. Since there can be a lag between the event creation and the creation of the email notification, it is possible that the values of notification variables have changed.
For example, suppose a notification uses the incident Assigned to field to determine who receives the notification. If the incident record is assigned to multiple people in succession, it is possible for multiple notification events to be placed in the event queue. However, when the events process job runs the Assigned to field only contains the value of the last person assigned.
The only way for a notification to contain state information for previous values is to use the parm1 and parm2 parameters available with event-based notifications. This is exactly what the incident.assigned event in the baseline system does by storing the values of the new and old users in event parameters. Depending upon your business needs you may need to create multiple event-based notifications to track record changes.