General/Object Oriented Programming: 'Generic Chat' object heirarchy diagram

please note the attached image...

I'm designing a class hierarchy for handling the complex internal structure of users, chatrooms, buddylist, sockets, etc. in a chat server. I plan to either make to project open source or at least the protocol.

This is the structure I was looking at using for the common library that contains all of the object that the server, client, and monitor all use.

Is there any way you can think of to improve upone this structure? Is the image too disorganized? Is there a simpler way? Keep in mind several of the classes will be serialized to XML for transfering over the network, and to binary for storage on the local medium.

No code please, just plain english or diagrams.

Looking to make this less complex, easier to understand.

I should add that Class User is to be serialized to xml for xfer across the network while Class UserRecord is to be serialized to binary for storage.

User holds basic info about the user, such as the user id and it's online status ("Online", "AFK", etc)

BTW, after posting, I noticed I made a mistake. PasswordHash as String will be a member of UserRecord, not User.