Documentation of principal attributes

I am looking for documentation on the attributes that can be set on a 
principal. The only thing I could find is page 233 of Jason Garman's 
"Kerberos: The Definitive Guide" from 2003.

The kadmin page *lists* the attributes, but is there a man page or 
Heimdal document page that *describes* what each attribute does and how 
it affects the principal?

Thanks, Adam Lewenberg