Address Book vocabulary...

Can anyone direct me to an xml vocabulary that is designed to encode 
address book-style, or human-directory information? I'm thinking of 
designing an address book client app that will need to communicate with 
several yet-to-be-determined external datasources. I figure if i make 
the client communicate in a standard xml human-resource directory 
format using soap or xml-rpc, i can just hide each datasource behind a 
servlet that will communicate with the client.

I'd like to use a standard vocab for the human directory information if 
possible rather than my own. I know enough to realize that designing an 
xml application for even something as simple-sounding as address book 
info is best left to the experts. Plus maybe we can gain some 
interoperability with other tools in the bargain.

Looking for a vocab that will include the usual info... name, multiple 
addresses, phones, emails, etc...

THANKS!

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Todd Ditchendorf, Web Developer
Email: 
Web  : http://www.ditchnet.org
Cell: (205) 243-9318