Every data-guard message in f that the caller must resolve, in DFS order, each message once at its first position. Auth leaves give no message.
Every data-guard message in f that the caller must resolve, in DFS order, each message once at its first position. Auth leaves give no message.
Conjunction: the messages of all its parts — every part must pass.
Disjunction: only the messages of its first branch (in declared order) that has a data leaf — any one branch is enough to pass, so joining the branches would ask for every alternative.
The head is always firstDataMessage(f), the message decide reports as Rejection.Invalid.