Notations / PKA

[Sven Radde]

Hi GnuPG-Users!

Is there anywhere a list of notations that do currently have any kind of
"canonical" meaning (or, rather, are interpreted by GnuPG and/or popular
MUAs in any way)?
I found out about "pka-adress at gnupg.org=..." and a quite old notation
that tells the commercial PGP about PGP/MIME capabilities but that seems
to be it.

PKA seems to be an interesting feature btw. Is it widely used?

cu, Sven