Like a document, a proof has a condition. The proof only becomes part of a case if the condition is true.
Typical examples of proofs are a passport scan, a wealth origin report or a company organisational chart. If e.g. a passport scan is required whenever a client is not Swiss, then the proof 'Passport Scan' would have a condition like this:
p is Person
p.nationality != che
Now every time, there is a person involved in a case who's nationality is not Swiss (che) Atfinity will ask to provide a scan of this person's passport.