A discrete identifiable possession, such as a piece of real-estate, to which its owner has legal title. For the Home Information Pack legislation the types of property are restricted to residential properties. It should be observed that "a property is a property is a property" and all real-estate properties, whether residential or commercial or whether being sold for the first or the nth time will have a very similar conceptual structure and similar rules and constraints. As such the broad description of a Property can be regarded as a framework, containing a set of extension points, that can be expanded as necessary to cover additional detail. Unique Property Reference Number An address is composed of a number of structured elements such as Postcode, Post-Town, Street etc. The District part of the Address. A District is an optional sub-part of the Post Town e.g. "Kings Heath" in "Birmingham" or "Ellington" in London. The Postcode for the Address Unique Property Reference Number - a 10-digit numeric string unmiquely identifuying each Property that may have a HCR registered against it. This is the primary key definition for the Property class - used when a message requires a reference to a Property to be passed rather than the details.