I used to be pretty interested in this kind of thing (the semantic web and all that), though I haven't been paying much attention to it lately.

I think the biggest benefit is not in updating mapping one's personal beliefs (though that does have some value), but in having shared belief networks to map reasons for disagreements (or even whether there is a disagreement at all).

I would be interested in helping design such a tool (and I second buybuydandavis's recommendation to look into Bayesian Belief Networks).