syntax for 2 dimensional multivalued attributes?

["Bennett, Steve" <S.Bennett@lancaster.ac.uk>]

Hi,

I'm trying to store some attributes with a bit more structure than simple key:value pairs. There seems to be a bit of a precedent in the Cosine otherMailbox attribute, but I don't really understand what's going on - can anyone give me any pointers?

What I'm trying to represent is a single username that could have access to multiple mailboxes on different mail services; each mailbox could receive mail via different mail addresses.

For example, user1 could have a mailbox on mailservice1 and another one on mailservice2, with user1a@example.org being delivered to her username on mailservice1 and user1b@example.org being delivered to her username on mailservice2, so I'd aim to have attributes that look something like:
  dn: uid=user1,ou=orgunit,dc=example,dc=org
  uid: user1
  othermailbox: mailservice1 $ user1a@example.org
  othermailbox: mailservice2 $ user1b@example.org

The point is that I want to preserve the mapping between email addresses and email services in a way that's not possible with a straightforward multivalued attribute, and this seems to be too trivial a problem to bother with additional objects to represent the additional complexity.

I could just stuff the data into a printable string and leave it to the client to sort it out, but it looks like there's a way to do this properly, if only I can find some documentation or examples.

Steve.