I’ve playing with something vaguely similar to your tripletags. I’m taking the approach of trying to map tags to a collaboratively developed ontology (and hopefully thereby be able to make interesting inferences). I’ve struggled a bit with the tag sense issue also - e.g. I’ve gone back and forth on whether or not the relationship between ontology elements and tags is inverse functional (which maps to the question of how to deal with multiple tag senses). Anyway, thought you might be interested in checking it out - it’s at:

http://labs.intellidimension.com/ontag/

Geoff