|This article does not cite any sources. (December 2009)|
The complexity of the notification system may vary.
Emergency notification systems may take advantage of modern information technologies.
In the event of a fire, or any emergency that requires human intervention, notification systems can provide a way of accepting feedback. The feedback can be used to determine what tasks the system should perform. For example, a chief firefighter, when notified of a pending fire, must acknowledge that the truck is en route, thus eliminating the need for further notifications.
Priority / pre-emption
Somewhat related to real-time interaction, above, certain notifications may bear more importance than others (for example, a fire alert would be more important than a cafeteria menu notification). Such types of notification would need to override any existing notifications of a lower priority.
The criticality of an event might change before the event is finally resolved. Sometimes a small failure may trigger a chain of failures that can lead to events that require immediate attention. For example, an e-mail that fails to send is not a significant error, and may be classified as a warning. However, the original incident that noted the e-mail failure may spawn a ping of the mail server responsible for relaying the e-mails. If the ping fails, the event may be escalated to a severe level, to indicate that a more important issue requires resolution.
When cellpone the list of recipients to notify of an event, a notification system might take into consideration the hours in which a recipient can be notified. Someone working a midnight shift may be available for handling emergencies between 11:00 pm and 7:00 am. The system should make no attempt to notify this person outside of those hours. A notification system could take into consideration vacation times, weekends, holidays, and so forth, to prevent notifying people when they are not available .
If a notification system cannot contact the intended party, often it is not sufficient to let the matter drop. In the previous example, the chief firefighter was informed of a pending fire. However, if the chief was assisting a tree-bound cat, the notification might not reach its target. Consequently the system must find another person to notify, typically by scanning a predefined roster.