Change detection and notification

Change detection and notification (CDN) refers to automatic detection of changes made to World Wide Web pages and notification to interested users by email or other means. Whereas search engines are designed to find web pages, CDN systems are designed to monitor changes to web pages. Before change detection and notification, it was necessary for users to manually check for web page changes, either by revisiting web sites or periodically searching again. Efficient and effective change detection and notification is hampered by the fact that most servers do not accurately track content changes through Last-Modified or ETag headers. A comprehensive analysis regarding CDN systems can be found here. Change detection and notification (CDN) refers to automatic detection of changes made to World Wide Web pages and notification to interested users by email or other means. Whereas search engines are designed to find web pages, CDN systems are designed to monitor changes to web pages. Before change detection and notification, it was necessary for users to manually check for web page changes, either by revisiting web sites or periodically searching again. Efficient and effective change detection and notification is hampered by the fact that most servers do not accurately track content changes through Last-Modified or ETag headers. A comprehensive analysis regarding CDN systems can be found here. In 1996, NetMind developed the first change detection and notification tool, known as Mind-it, which ran for six years. This spawned new services such as ChangeDetection (1999), ChangeDetect (2002), Google Alerts (2003), and Versionista (2007) which was used by the John McCain 2008 presidential campaign in the race for the 2008 United States presidential election. Historically, change polling has been done either by a server which sent email notifications or a desktop program which audibly alerted the user to a change. Change alerting is also possible directly to mobile devices and through push notifications, webhooks and HTTP callbacks for application integration.