Notes on Annotea

by Edd Dumbill

The last day of WWW10 was given over to Developer's Day, which offered the
chance for developers working on web technologies to share and discuss details
of their projects. I attended the Semantic Web day, where in the morning
several W3C Team members showcased href="">Annotea, their tool for annotating
web pages.

Annotation isn't new, and there have been several attempts at it so far on
the web. One of these was the controversial (and now defunct) href="">Third Voice, allowing post-it note style
adornment (some might say defacement) of pages. Annotea takes a slightly
different approach, being non-proprietary and based on open web standards.

Annotea is basically an annotation server: it uses an RDF database and a
simple HTTP front end to store annotations, and respond to annotation queries.
The W3C has deployed an Annotea server at href="">, but anybody is
free to deploy one -- so you can have multiple sources of annotation.

In order to view or add annotations, you need a user agent which supports
them. Amaya, the W3C browser/editor, has pretty sophisticated support for
annotations, and is a good place to start experimenting.

Work is in progress to make other tools understand how to manipulate these
annotations. As well as a href="">servlet/JavaScript
interface, there's the href="">Annozilla project, which adds a
sidebar to the Mozilla browser to display annotations.

Taking a look under the hood, Annotea is quite simple to understand. It
uses an RDF schema to
define the properties of an annotation, and is reasonably easy to read and
figure out what's
going on
. A fun and relatively simple experiment might be to get a weblog
or comment-system to export its content in Annotea format, and therefore show
up in annotation-aware user agents.

Annotea is designed so you there can be any number of annotation servers.
This recognizes the decentralized nature of the web, and means you can switch
in annotations from your trusted sources, or for instance, in a corporate
setting, ensure your annotations get no further than your own intranet.