A web annotation is an online annotation associated with a web resource, typically a web page. With a Web annotation system, a user can add, modify or remove information from a Web resource without modifying the resource itself. The annotations can be thought of as a layer on top of the existing resource, and this annotation layer is usually visible to other users who share the same annotation system. In such cases, the web annotation tool is a type of social software tool. For Web-based text annotation systems, see Text annotation.
Web annotation can be used for the following purposes:
to rate a Web resource, such as by its usefulness, user-friendliness, suitability for viewing by minors.
to improve or adapt its contents by adding/removing material (like wiki).
as a collaborative tool, e.g. to discuss the contents of a certain resource.
as a medium of artistic or social criticism, by allowing Web users to reinterpret, enrich or protest against institution or ideas that appear on the Web.
to quantify transient relationships between information fragments.
Annotations can be considered an additional layer with respect to comments. Comments are published by the same publisher who hosts the original document. Annotations are added on top of that, but may eventually become comments which, in turn, may be integrated in a further version of the document itself.
Standardisation efforts
The W3C has a Web Annotation Working Group which has issued 3 Recommendations:
Web Annotation Data Model
Web Annotation Vocabulary
Web Annotation Protocol
The W3C also had a previous web annotation standardisation effort, Annotea (see below), which was conceived of as part of the semantic web.
Many of these systems require software to be installed to enable some or all of the features below. This fact is only noted in footnotes if the software that is required is additional software provided by a third party.
The earliest web annotation system was probably CritLink, developed in 1997-98 by Ka-Ping Yee of the University of California. CritLink worked as an HTML "mediator", hence not requiring additional software or browser extensions but having limited support for modern JavaScript-driven websites.
Annotea - a W3C project that tried to establish a standard for web annotation.
ThirdVoice - a system launched in 1999 that shut down due to lack of success in April 2001.
Wikalong was a Firefox plugin created in 2004 that provided a publicly editable mediawiki page in the margin of any webpage. (It was later accessible in other browsers via a bookmarklet.) Common uses were note-taking and discussion about the website. On Google, the Wikalong margin provided a variety of useful tips and shortcuts for searching. The project was discontinued in 2009 when the storage wiki went offline. It had been suffering from link spam abuse.
Fleck* - launched in 2005 with much publicity as a stick-it notes application for the web. A patent, funding and marketing didn't stop it from failing. Discontinued in 2010.
stet was the Gplv3 comment system.
Crocodoc, launched in 2007, dabbled in web page annotation as part of its broader mission. It was originally developed in Adobe Flash. It was acquired by Box.com in 2013 and the web annotation side of it was shut down two years later.
ShiftSpace, started in 2008, was a tool for artistic and political subversion and reimagining of websites - development stopped in 2011.
Blerp, launched in 2009, was a multimedia, extensible tool for annotating web pages with widgets viewable by any other Blerp user.
Google Sidewiki, launched in 2009, was part of Google Toolbar, and allowed users to write comments alongside any web page. It was discontinued in December 2011.
Dispute Finder was built by Rob Ennals while working for Intel. It attempted to automatically identify disputed claims on websites, highlight them, and link to comments and pages which corrected the dispute.
SharedCopy was an AJAX based web annotation tool that allowed users to mark-up, highlight, draw, annotate, cache, sticky-note and finally share any website.
