I've been lurking on this thread because It's an interesting topic. But I'm not sure it really belongs here. Multivalued logic is a very deep topic which has been studied in depth for the last ~150 years by some of the best mathematicians who ever existed. It's not clear to me how much we can realistically add to this. boost tribool implements the most widely accepted interpretation of 3 valued logic in a manner which users would expect. And its usage and purpose is well explained in it's documentation. So the question arises - what else is here for us to mine? Just taking a cursory look at literature in this area, it would seem that there is likely something interesting for us here. So if one wanted to implement one or more if the multivalued logics already studied along with a good document describing use cases and limitations that I think would be interesting. But spending huge amounts of time trying to agree on some particular usage seems to me sort of overkill - but maybe not - after all it's fun and interesting to talk about. But I'm skeptical that this would lead to something like a useful boost library. Robert Ramey