affinity, cf and so on

[Jan.Wieringa at ALGEM.PT.WAU.NL]

I wonder if anybody can give me comment on my following problem:

When some people are identifying plants or animals and have doubt about the
correctness of their identification, they put "aff." or "cf." before the name.
Some people say that the cf. means they just don't know if the name is correct,
while aff. means that the specimen seems most closely related to the attached
name, but that it certainly is not that species (in most cases they mean it
might represents a new species). Other people however think it works exactly
the other way round (so cf. would mean certainly not this species). Can anybody
tell me which option is the correct one, and has anybody published a definition
of con forma or affinis in the taxonomic context?

Jan J. Wieringa      (Jan.Wieringa at algem.pt.wau.nl)