If I have a multi-state input that is currently unknown (i.e. I don't have enough information to compute its state) should I set Reliability to Reliability.multiStateFault ? Basically I'm looking for a way to indicate "unknown" without having to define a completely separate state for "unknown" (as that would be confusing here - what I'm building is really more of a proxy to an existing system).

I'm having trouble, even within the bacnet spec book, figuring out how I'm really supposed to use MultiStateFault.