For a given change B, the input to condition inference is the set of pairs u, k , where u k is a phone trigram in some underlying form and the label k can be positive ( ), negative (⊥), or unknown (?).
by contrasting examples in the first column, we infer that the insertion happens when the suffix /z/ occurs after a strident (like /s/ in /mIs/); otherwise, /z/ and /d/ are devoiced whenever they occur after a voiceless obstruent (like /p/ in /zIp/).