Sun Microsystems Internet Message Access Protocol (IMAP) allows nomadic users to access their mail store from any client, but it does not support storage of personal addressbooks. Application Configuration Access Protocol (ACAP) provides a mechanism for storage of personal addressbooks. While ACAP permits the definition of vendor specific solutions to this problem, having a documented addressbook dataset class permits clients from different vendors to interoperably share the same personal addressbooks. This specification defines an ACAP dataset class for personal addressbooks.