A zone namespace is a list of zones, split into one or more files. Files load in asciibetical order, with zones from earlier files overriding those in later files. Zones higher up in a namespace file override zones lower down in the same namespace file, but namespaces are independent of each other - overlapping zones in separate namespaces will both be in effect. You may also insert a reference (#ref) to a reference zone namespace file in the place of a zone to insert its contents at that point in the current file.