We are certainly not the first project to begin to start to commence to create a Web-based annotation system.
Learning from the past will help us find our way to (and through) the future.
At Apache
Hypothes.is Historical Survey of Annotation Efforts
Below is a rough outline for what this page could/should/may hold...your input is most welcome!
...table of earlier attempts
...links to any and all other (Web) annotation tools
...events (past, present, and future) related to annotation