Configuring Shared Mailbox Dictionaries

[james at lottspot.com]

Hello, list!

I am in the midst of configuring a new Dovecot IMAP server, and I'm 
preparing to setup shard mailboxes as part of the ocnfiguration. In 
order to get these setup the way I want, I've figured out that I'm going 
to have to setup an acl_shared_dict. This is where things start to get 
confusing for me, as I have had difficulty finding thorough explanations 
of dictionary configuration.

My primary concern is that all my user details are stored in a sqlite 
database in which the '%n' and '%d' components of username/email 
addresses are stored in separate columns. The SQL dictionary example in 
the Shared Mailboxes document 
[http://wiki2.dovecot.org/SharedMailboxes/Shared] assumes that the 
username is stored as a singular '%n@%d' key. In my authdb lookups, I 
use sqlite syntax to concatenate the '%n' and '%d' columns around a '@' 
character to find the user. Is it possible to implement an 
acl_shared_dict in some similar fashion?

My second question, which is completely unrelated and more out of morbid 
curiosity than anything (although it could affect my configuration 
decisions) is that I noticed every dictionary which shows up in the 
documentation has a "pattern" field. In the case of the acl_shared_dict 
example, the pattern is 'shared/shared-boxes/user/$to/$from'. I couldn't 
figure out by studying the example where this value was derived from, or 
indeed where it is derived from in any example dictionaries which are 
documented. Can anyone explain the meaning of the "pattern" field and 
what exactly its value means?

Thanks in advance for all your helpful answers! :)