Web annotation

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

Web annotations were first standardised on February 23, 2017 with the release of three official Recommendations by the W3C Web Annotation Working Group:

• 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.

Comparison of web annotation systems

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.

Features

Annotation system	Private notes	Private group notes	Public notes	Notification	Highlighting	Formatted text	Archives	Viewing annotations	API	License	Notes
A.nnotate	Yes	Yes	No	Yes	Yes	No	Yes		Yes	Proprietary	Can annotate PDF, ODF, .doc, .docx, images, as well as web pages (but only a limited number in the free version)
Diigo	Yes	Yes	Yes	Yes	Yes	No	Yes		Yes	Proprietary	Public annotations are only allowed for established users. Group tag dictionary feature to encourage tagging consistently within a group.
Firefox (built-in)	Yes	No	No	No	No	No	No	Bookmark properties	Yes	MPL	"Description" and "tags" fields of bookmarks provide this
Genius	No	Yes	Yes	Yes	Yes	Yes		Chrome, via genius.it	Yes	Proprietary	Genius has a Chrome Extension, an iPhone App, and a subdomain (genius.it/) which you can prepend to any domain to annotate. This is in addition to their website, genius.com, where users can annotate lyrics, literature, news, and other categories.
Hypothes.is	Yes	Yes	Yes	Yes	Yes	Yes		Chrome, via.hypothes.is	Yes	MIT, BSD	In February 2015, different features were announced, such as private group annotation, semantic tagging, moderation, etc.
Org-mode (with extensions)	Yes	No	No	No	No	Yes	No		Yes		Emacs-based; requires technical knowledge to set up; not as user-friendly as some other solutions; non-Latin characters allowed in notes but not in tags

Discontinued web annotation systems

• An early version of the Mosaic browser was tested with collaborative annotation feature in 1993 but never passed the test state.
• 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.
• Delicious was founded in 2003 and provided cloud bookmarks with optional descriptions (a form of annotation) of up to 1000 characters. It was rumoured that it would be shut down in 2010, but it was only actually finally shut down in 2017 when it was acquired by Pinboard, a competitor.
• 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.
• Stickis, launched in 2006, focused primarily on tight-knit communities, and allowed them to create a blog of annotations.
• 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.

See also

• Comparison of notetaking software
• Social bookmarking
• Some reference management software packages also support web annotations
• Backlinks
• Online deliberation
• Folksonomy
• Metadata
• Threaded discussion
• Virtual graffiti
• Comparison of software saving Web pages for offline use

Further reading

• Sanderson, Robert; Van de Sompel, Herbert (2010). "Making Web Annotations Persistent over Time". Proceedings of JCDL '10, Joint Conference on Digital Libraries. Association for Computing Machinery. pp. 1–10. arXiv:1003.2643. doi:10.1145/1816123.1816125. {{cite conference}}: Unknown parameter |booktitle= ignored (|book-title= suggested) (help)
• Signer, Beat: "An Architecture for Open Cross-Media Annotation Services", Proceedings of WISE 2009, 10th International Conference on Web Information Systems Engineering, Poznan, Poland, October 2009
• On Web Annotations: Promises and Pitfalls of Current Web Infrastructure. Venu Vasudevan and Mark Palmer, Proceedings of the 32nd Hawaii International Conference on System Sciences - 1999
• A Survey of Web Annotation Systems. Rachel M. Heck, Sarah M. Luebke, Chad H. Obermark. 1999.
• New ways of using Web annotations. Laurent Denoue, Laurence Vignollet.
• Ricardo Kawase, George Papadakis, Eelco Herder, Wolfgang Nejdl: The impact of bookmarks and annotations on refinding information. ACM Hypertext Conference 2010: 29-34
• Ricardo Kawase, Eelco Herder, George Papadakis, Wolfgang Nejdl: In-Context Annotations for Refinding and Sharing. Webist (Selected Papers) 2010: 85-100

External links

• W3C Web Annotation Working Group Recommendations (as of February 23, 2017):

1. Web Annotation Data Model
2. Web Annotation Vocabulary
3. Web Annotation Protocol

• Web Annotation Architecture, W3C's interactive illustration