In the UK local authorities have responsibility for creating all addresses and to maintain the Local Land and Property Gazetteer (LLPG) address database.
http://en.wikipedia.o...nd_Property_Gazetteer
The British Standard for the structure of addresses is BS7666.
An Addressable Object in BS7666 terms is a real world object that has a fixed location and which may be identified and referenced by means of one or more addresses. A Primary Addressable Object Name (PAON) is simply the name given to an addressable object that can be addressed without reference to another addressable object, for example a building name or street number.
http://xml.coverpages.org/bs7666.html
The Primary Addressable Object Name (PAON) is the designated premise number, and/or the premise name, where neither of these exist then the PAON is the name of the organisation in occupation, or a description of the addressable object.
http://interim.cabine..._address/primary.aspx