Change detection and notification: Difference between revisions

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{{Short description|Automated reporting of web page changes}}

'''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 engine]]s 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 [[HTTP ETag|ETag]] headers.

{{Distinguish|content delivery network}}

'''Change detection and notification''' ('''CDN''') is the automatic detection of changes made to World Wide Web pages and notification to interested users by email or other means.<ref>{{Cite book|last1= Mallawaarachchi|first1=Vijini |last2=Meegahapola |first2=Lakmal |last3=Alwis |first3=Roshan |last4=Heshan |first4=Eranga |last5=Meedeniya |first5=Dulani |last6=Jayarathna |first6=Sampath |url=http://worldcat.org/oclc/1201518429|title=Change Detection and Notification of Web Pages: A Survey|date=2020-05-14|oclc=1201518429|doi= 10.1145/3369876|arxiv=1901.02660|bibcode=2019arXiv190102660M|s2cid=57759312 }}</ref>

'''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 engine]]s 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 [[HTTP ETag|ETag]] web-server headers. In 2019 a comprehensive analysis regarding CDN systems was published.

==History==

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]].<ref>{{cite web |title=To the Wayback Machine, Sherman!|url=https://www.economist.com/democracy-in-america/2008/07/16/to-the-wayback-machine-sherman |publisher=[[The Economist]] |accessdateaccess-date=9 January 2019}}</ref>. 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 notification]]s, [[webhooks]] and HTTP callbacks for application integration.

Monitoring options vary by service or product and range from monitoring a single web page at a time to entire web sites. What is actually monitored also varies by service or product with the possibilities of monitoring text, links, documents, scripts, images or screen shots.

With the notable exception of Google's patent filings related to [[Google Alerts]], [[intellectual property]] activity by change detection and notification vendors is minimal.<ref>{{cite web |title=He created Google Alerts. Now he's an almond farmer |date=4 April 2016 |url=httphttps://money.cnn.com/2016/04/04/smallbusiness/naga-kataru-google-alerts/ |publisher=[[CNN]] |accessdateaccess-date=9 September 2016}}</ref> No one vendor has successfully leveraged exclusive rights to change detection and notification technology through patents or other legal means.{{Citation needed|reason=Just as one can not prove a negative, one can not cite sources that do not exist|date=September 2016}} This has resulted in significant functional overlap between products and services.

==Architectural approaches==

Change detection and notification services can be categorized by the [[software architecture]] they use. TwoThree principal approaches can be distinguished:

=== Server based ===

A server polls content, tracks changes and logs data, sending alerts in the form of email notifications, [[webhook]]s, [[RSS]]. Typically, an associated website with a configuration is managed by the user. Some services also have a mobile device application which connects to a [[cloud server]] and provides alerts to the mobile device.

=== Self-hosted based ===

A relatively newer approach, which lays between server-based and client-based is to use [[Self-hosting (web services)|self-hosting]], where the software which would normally run on a separate server runs on your own hardware locally, generally means that the software provides a miniature [[web server]] with a browser interface instead of a classic [[graphical user interface]] provided by an application.

=== Client based ===

A local client application with a [[graphical user interface]] polls content, tracks changes and logs data. Client applications can be browser extensions, mobile apps or programs.

==Considerations==

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==References==

{{Reflist}}

* {{Cite book | last1 = Chakravarthy | first1 = S. | last2 = Hara | first2 = S. C. H. | chapter = Automating Change Detection and Notification of Web Pages (Invited Paper) | title = 17th International Conference on Database and Expert Systems Applications (DEXA'06) | pages = 465 | year = 2006 | isbn = 0-7695-2641-1 | doi = 10.1109/DEXA.2006.34| s2cid = 6395251 }}

* {{cite journal |lastlast1= Shobhna|firstfirst1=Bansal |last2=Chadhaury |first2=Manoj |date=June 2013 |title=A Survey on Web Page Change Detection System Using Different Approaches |url=http://www.ijcsmc.com/docs/papers/June2013/V2I6201391.pdf |journal=International Journal of Computer Science and Mobile Computing |publisher=IJCSMC |volume= 2 |issue=6 |pages=294–299 |doi= | issn=2320-088X |access-date=8 September 2016}}

*[https://github.com/dgtlmoon/changedetection.io changedetection.io github] Self-hosted website change detection and notification

[[Category:Change detection and notification| ]]

[[Category:World Wide Web]]