Web annotation
Web annotation refers to
- online annotations of web resources such as web pages or parts of them, and
- a set of W3C standards developed for this purpose.
Annotation of web resources
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.
- 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.
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.| Annotation system | Private notes | Private group notes | Public notes | Notification | Highlighting | Formatted text | Archives | Viewing annotations | API | License | Notes |
| A.nnotate | Proprietary | Can annotate PDF, ODF,.doc,.docx, images, as well as web pages | |||||||||
| Diigo | Proprietary | Public annotations are only allowed for established users. Group tag dictionary feature to encourage tagging consistently within a group. | |||||||||
| Firefox | Bookmark properties | MPL | "Description" and "tags" fields of bookmarks provide this | ||||||||
| Genius | Chrome, via genius.it | Proprietary | Genius has a Chrome Extension, an iPhone App, and a subdomain 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 | Chrome, via.hypothes.is | MIT, BSD | In February 2015, different features were announced, such as private group annotation, semantic tagging, moderation, etc. | ||||||||
| Org-mode | 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
| System | Notes | Date Discontinued |
| Mosaic Browser | An early version of the Mosaic browser was tested with collaborative annotation feature in 1993 but never passed the test state. | Never passed the test state |
| CritLink | Perhaps the earliest web annotation system. 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. Annotea was conceived as part of the semantic web. According to the website, Annotea development stalled in October 2005. | |
| ThirdVoice | A system launched in 1999. It was targeted by a campaign called Say No to TV, led by independent web hosts which likened ThirdVoice to "Web graffiti." It was shut in April 2001 because it couldn't generate enough advertising revenue to stay in business. | April 2001 |
| Delicious | Founded in 2003 and provided cloud bookmarks with optional descriptions 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. | 2017 |
| Wikalong | A Firefox plugin created in 2004 that provided a publicly editable mediawiki page in the margin of any webpage. 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. | 2009 |
| 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. | 2010 |
| stet | 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. | 2009 |
| Blerp | Launched in 2009. A multimedia, extensible tool for annotating web pages with widgets viewable by any other Blerp user. | |
| Google Sidewiki | Launched in 2009. A part of Google Toolbar that allowed users to write comments alongside any web page. It was discontinued in December 2011. | December 2011 |
| SharedCopy | An AJAX based web annotation tool that allowed users to mark-up, highlight, draw, annotate, cache, sticky-note and finally share any website. |
Web Annotation standard
In the Web Annotation standard,The basic data structures of Web Annotation are
- target,
- body, and
- annotation
Web Annotation was standardized 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
- Embedding Web Annotations in HTML
- Selectors and States
Note that this ontology defines the Web Annotation namespace, and that this namespace is conventionally abbreviated as
oa. This is the abbreviation for Open Annotation, a W3C Community Group whose specifications formed the basis for the Web Annotation standard.Web Annotation supersedes other standardization initiatives for annotations on the web within the W3C.
Related specifications
Web Annotation can be used in conjunction with fragment identifiers that describe how to address elements within a web document by means of URIs. These includeOther, non-standardized fragment identifiers are in use, as well, e.g., within the NLP Interchange Format.
Independently from Web Annotation, more specialized data models for representing annotations on the web have been developed, e.g., the NLP Interchange Format for applications in language technology. In early 2020, the W3C Community Group `Linked Data for Language Technology´ has launched an initiative to harmonize these vocabularies and to develop a consolidated RDF vocabulary for linguistic annotations on the web.