The Annotation Engine is a set of Perl scripts and a database that allows readers anywhere to add comments to web pages anywhere else. The comments, URL, and location pointers are stored in the database here, enabling the Annotation Engine to add them to a page before it is displayed. The engine does not copy the remote web page itself, only adds its extra information to the HTTP stream when it is called to proxy a page.
The Annotation Engine is a tool in development. In online and classroom courses, teachers may use the engine to mark selections of web pages as recommended or required reading, and students may add notes for themselves or the class. It is also being used in the Openlaw project for public comment on working drafts.
Unlike the now-defunct Third Voice, this engine does not require a browser plugin. Instead, like the CritLink Mediator from which it takes inspiration, it is a server-based proxy. This design allows its notes to be viewed in any browser, on any computer.
The Annotation Engine is Free Software. The source code in progress is available here. It requires Perl, the LWP::UserAgent package, HTTP::Parser, Date::Manip, and mySQL. Visit the Sourceforge project page for more development information.