A floor is a subdivision of a building.  

A floor can be contained by a Structure Junction InstallationSite/BuildingRootElement or InstallationSite/StationRootElement.

A floor cannot contain an Aisle. A Floor can contain Room, Rack, or Apartment. A floor can contain any Communication Junction Object

A room is a subdivision of a building.

A room cannot contain a Floor

A room can contain an Aisle, a Rack and any Communication Junction Object.

Aisles are a subdivision of a room.  In exchange buildings, Racks are often referenced by their Floor, Room, AIsle, and Bay position.  

An Aisle can only contain a Rack or any Communication Junction Object.

An apartment cannot contain another junction object.

An apartment can only contain a Communication Junction Object of Equipment or Chassis Asset Group