LDAP schema for dovecot proxy?

[Andrey Fesenko]

Hello,
I want to deploy dovecot proxy/director with the backend and
authorization in LDAP. Dovecot wiki specifies only what is necessary
to apply additional arguments that the scheme would have earned a
proxy, but no solid LDAP schema.
Is there such a scheme, such as the existing scheme

http://www.zytrax.com/books/ldap/ape/courier.html
http://pro-ldap.ru/sources/schema/qmail.schema
http://open.rhx.it/phamm/schema/phamm.schema

Unfortunately for the tasks they are not good because they just no
dovecot-specific variables