Then use a "real" directory system, like the UDD. It's neither X.500 nor
Standard in any way, but it exists and works, today. It's not very well
documented but then it's not the only thing which is not very well
documented either. There have already been several changes to the SIGNUP
FILE contents and exact format since /WHOIS was written, fortunately none
of them happened to create any problem for /WHOIS but it should be clear
that SIGNUP FILE was never meant to be used as a directory service, and
its format can change at any time for performance or usability
considerations.
Eric