[naveen99]

For 3 values, don’t you just need a pair of booleans ? Known or unknown… If known: 0 or 1 …

[epolanski]

unknown | yes | no has the same cardinality (3) of unknown | boolean as you can replace boolean with yes | no.

If you write code that has to handle it, you still need to consider 3 cases, you can never reduce it to two cases only.