"Address book" will be abbreviated as "ADB" from now on.
The ADB classes stor and allow to retrieve/edit e-mail addresses indexed by aliases/nicknames and other related information. It's important that ADB records are hierarchally organized, i.e. there may be not only entries but also groups containing other entries and groups. There may be several address books, possibly in different formats.
FIXME: what happens if the same nick is found in several ADBs?