[Dovecot] Syntax of pattern in map section

[da-dovecotlist-15 at abelonline.de]

I can't seem to find any documentation on the meaning/syntax of the "pattern" variable in map sections that are found in dovecot-dict-sql.conf.ext for example. I am trying to setup shared folders.

The only thing[1] I found is:
>>First you'll need to know what kind of dict paths the code uses. ACL
>>plugin uses these paths:
>>
>>shared/shared-boxes/anyone/$owner
>>shared/shared-boxes/user/$user/$owner
>>shared/shared-boxes/group/$group/$owner

What is a "dict path"? Is this some kind of hard coded identifier in the Dovecot code?

I need to understand how they work because I can't use the example in http://wiki2.dovecot.org/SharedMailboxes/Shared. This is because in my PostreSQL table users are not a single column but two columns with the local and domain part[2]:

        Table "public.shared_mailboxes"
        Column         |          Type          
-----------------------+------------------------
 shared_mailbox_local  | character varying(64)  
 shared_mailbox_domain | character varying(253) 
 shared_to_local       | character varying(64)  
 shared_to_domain      | character varying(253)

How should a map section look in this case?

[1]http://www.dovecot.org/list/dovecot/2009-April/038922.html
[2]I did this in order to use REFERENCES to ensure the user exist.

Kind regards