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What Does Notification Services Do?

SQL Server 2005

A Notification Services application (or "notification application") generates and sends messages to users or other applications that have subscribed to the application. To understand notification applications, it is important to define key terms:

  • A subscriber is a person or application that subscribes to and receives notifications.
  • A subscription is a request for specific information, such as a stock price or the scores of a sports team, to be delivered to a particular device, such as an e-mail address or cell phone.
  • An event is a piece of information, received by the notification application, that subscribers might be interested in. A stock price at a specific time is an event, as is a sports score, or a product delivery message. Almost any real-world occurrence can be expressed as a Notification Services event.
  • A notification is a message that contains information related to a subscription. A notification might contain a message about a new high value for a specific stock or the final score for a game.

The following illustration shows the basic operation of a Notification Services application.

Basic operation of Notification Services

The application produces notifications as follows:

  1. Subscribers create subscriptions related to the application.
  2. The application collects events.
  3. Notification Services matches subscriptions to events.
  4. When an event and subscription match, Notification Services generates a notification.
  5. Notification Services then formats the notification and sends it to a the device specified in the subscription.

A good example of a notification application is a stock application. A subscriber could create a subscription to be notified about stock ADCP if the stock price goes above 70, and to receive the notification on a cell phone.

The notification application collects stock data from a stock ticker. Each time a batch of stock price "events" arrives, Notification Services compares subscriptions to the current set of events. If stock ADCP is above 70, Notification Services creates a notification, formats it, and sends it to a delivery service that forwards the message to the subscriber's cell phone.

Notification Services provides features to avoid sending duplicate notifications. For example, you can record that a specific subscriber already received a notification for stock ADCP. If the next stock price for ADCP is also above 70, your notification logic can cancel further notifications to the subscriber.

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