A map consists of zones, which are of variable size, geometry, and description. A zone should be defined as any space(physical or abstract) that is discrete from others. The basic rule in considering if a feature on the map warrants its own zone is if it would make a diffrence to be there or not, then it is a zone. Considering an indoor map, a room with walls and a door is definitely a zone, but a huge room may be split up into multiple zones, because it would matter which end of the room you are in. In an outdoor map with huge spaces, that whole building may be represented as a single zone because all that matters is if you are inside the building or not.