Selective dissemination of information

As Alert Service (of English. Alert service for message service or message service), Selective Dissemination of Information (SDI ) or current awareness services are information services refer to operations where requests can be filed after the publish-subscribe model, the answers to are then sent as regular messages. The messages can be, for example, of a search engine, posts on a weblog or tables of contents of journals. The messages can be received here via RSS or email.

Unlike search engines, which is searched in all documents have been collected, determine alert services continuously whether a newly added document previously Come meets defined query criteria and may send a message to the user. The message contains either the full results, a summary or a reference.

Generally found in current awareness services, the notification at regular intervals - for example, monthly - instead, while newly added records trigger the notification of an alert service. However, the terminology is not uniform, so that different names for the same kinds of services are used. In a greatly expanded the meaning of the term alert is also used for services in which it is merely subscriptions periodically appearing publications. For example, some journal publishers call the subscriptions of digital contents are also " alerts ".

History, technology and dissemination

A preform of alerting services form abstracting journals, review the new publications. Computer-based alert services are known about since the early 1970s.

From about 1999 won weblogs as a new form of publication on the Internet in importance. Blogs typically have an RSS feed that makes all contributions directly related to the publication in machine-readable form accessible. Blog pings ensure that interested weblogs, but also eg Learn Alert services immediately automated by the publication of each new post. In 2002, the weblog Alert Service Technorati arose. Technorati reported about new posts in weblogs that meet user-defined query criteria. Just a year later created numerous similar services since 2004 to integrate the large, established Internet search engines like Google, Yahoo and MSN alert services in their offer. Meanwhile, the major search engines offer, for example, to also alert services specifically for traditional news sources, so for agency Scores, online editions of newspapers and similar sources; and with IngentaConnect 2004 Alert Service for tables of contents of scientific journals emerged.

Application Examples

Search Engine

In addition to the alert services to search in weblogs prospective research is also offered by search engines. Prospective search engines signals position changes in the top results of a given search query. For a quite special information needs are met: For example, observe whether their own website is among the top results in the search for the generic name of the product marketed a company. Another case would be as sharp aggregate query that initially less than ten or twenty results are achieved - in this case, the prospective requirements would also report on entirely new sites. The Yahoo Web search as well as the news and Web search by Google offer - to alert services, they deliver the results both as an RSS feed and as an e -mail notification - in both its international and German versions.

Duration search

Commercial database providers offer the possibility of continuous research with its own thematic queries in databases to be selected. The contents of the databases are mostly specialized publications, patents, etc. The queries must be created in the search language provided by the database vendor. The duration searches are free of charge, when prompted many parameters as content of the issue ( database fields ), duration, quantity of publications, etc. can be specified.


In addition to the alert service, report the changes in a query criteria defined by the user, there are also services that satisfy a simpler function: you simply log every change a user-selected site, regardless of its nature and its contents. Because even with these services, the messages are event-driven, they can certainly be also referred to as alerts.

Social bookmarking services

DURL is an - albeit rather special - a "real " Alert service, which works with the data. DURL notified for example, if a particular URL has been tagged.