Dataflow editor technical concept, using Raphaël.js/SVG
You can try it live: http://linkbroker.hu/ihome/editor/
I want to select the best platform for a dataflow editor. If we choose browser-based GUI, Raphaël.js looks a good choice.
You can delete connection by starting a new connection from a pin, and if you go the same direction (+/- a small angle) with an existing one, it will be faded, which means "marked for deletion", then if you release the mouse button, it will be deleted. If there are more connections in the similar direction, the closest one will be selected - it sounds a good idea, but if you're over a target pin, it's better to be select the connection which ends at the target pin you're right over, not the closest one.