SQLServer 2005 Notifications Services

Overview of Notification ServicesNotification Services provides a framework for developing subscription-based applications through which users are notified about events.

Instances
A Notification Services instance is defined in an XML configuration file and implemented as a Microsoft Windows® service that stores its data in a SQL Server database. The instance stores subscriber data that can be shared across all of its applications, and controls the generation and delivery of notifications. The Windows service for an instance is named NS$instance_name and the database associated with the instance is named instance_nameNSMain

Applications
Each instance can control multiple applications. An application is defined in an XML application definition file (ADF) and implemented as a database named instance_nameNSapplication_name. Applications store information about events, subscriptions, and notifications.

The main features of Notification Services in SQL Server 2005 are described in here

Subscription Management ObjectsAn API for building subscription management applications through which users can subscribe to events.

Event APIsFour ways for event sources to enter event information into the system: a managed API, a COM-based API, an XML file–based API, and a stored procedure–based API.

Set-based subscription processingSet-based operations to relate events to subscriptions and generate notifications. This approach means that your notification application can use the performance and scalability of the SQL Server relational database engine.

Notification formatting and deliveryExtensible Stylesheet Language (XSL) to format notifications for multiple device types, and deliver them using an extensible delivery channel architecture. This allows notifications to be delivered to virtually any kind of device using any protocol.

This animation describes how you can use Microsoft® SQL Server™ 2005 Notification Services to implement subscription-based notification solutions. Notification Services is a framework for implementing applications that notify subscribers when specific events occur.
Notification Services solutions are configured using two kinds of XML file: a configuration file, which contains the settings for an instance of Notification Services, and application definition files, or ADFs, which contains settings for an individual notification application in that instance.
These files are used to define SQL Server databases; one for the instance, and one for each application. Events can be anything that a user might want to be notified about, such as a stock price change, an order shipment, or a goal scored in a soccer match.
Events are submitted to Notification Services by an event provider and stored in a database table.
Users register themselves as subscribers through a subscription management application, specifying details about the subscriber, subscription details for specific events, and information about devices that notifications can be sent to.
They can create subscriptions that send notifications as events occur, or at regularly scheduled intervals. Notification Services uses an internal generator component to match events to subscriptions and create appropriate notifications.
Because event data and subscription data are stored in tables, the generator can use set-based SQL queries to perform the matching operation extremely efficiently.
The notifications are then passed to an internal distributor component, which formats the notification appropriately and sends it to the devices specified by the subscriber. The notifications can be sent in various forms, including e-mail, SMS text messages, and .NET Alerts.