I’d like to build a proof-of-concept web-based database manager (such as the desktop version in the screenshot below) that has the following features.
The schema will be provided initially through a flat file.
It seems like HTML5 might be an option. What about non-HTML? What about processing.js? Are there any libraries I could/should take advantage? Is there already a service I can tap into?
Any opinions or advice would be appreciated!
Edit
Primary goal of the project is the build a protoype of the UI.

I’ve decided to use http://raphaeljs.com for the project. This SVG library supports older browsers and given this application is highly interactive with the user, it makes sense for me in this project to use SVG over Canvas.