A zone is an identified area or sub area of an asset. To help in locating different regions within Data Modules and identifying locations for maintenance planning, the Materiel is divided into areas and sub-areas known as zones. A zone is identified by a standard number consisting of three digits: NNN — used to indicate the major structural area of the Materiel NNN — indicates zones and on which side of the centre line (if any) the zone is located. NNN— used to indicate sub-zones. Note: Odd digits apply to left side facing forward, even digits to right side. Note: Sub-zones and Sub-Sub-zones are minor areas of larger zones. When you start to zone, the following general requirements should be adhered to: Fuselages should be zoned lengthways from forward to aft. Floors or decks should be zoned from upper to lower. Major structural components (entrance doors; cargo doors; landing gear and doors, etc) need to be allocated their own zone. Doors of any kind are themselves zones. Where possible zones should be confined to actual physical boundaries (fuselage/hull frames, turrets, bulkheads, etc). Internal boundaries, based on structural components like these, are generally more valuable when zoning. If any major structural changes occur to the materiel, a new zone designation will need to occur specific to the version. Zone boundaries and station numbers must be clearly identified on zone charts and each zone needs to be labelled with a physical description. Major components cannot be split when zoning. This is generally easier to achieve when zoning areas are clearly defined, such as a deck of a ship. Boundaries will incorporate related structures such as door frames. These type of zones shall not be shared between zones. The zoning information is contained within the ID Status section of a data module in the <pmd> tag. Within the <pmd> (Production management data) tag, the <prelreqs> tag then holds the zoning information within the <zone> tag. The suggested ‘zoning’ values, of the specification should be placed in this element. Note: Zoning information is present in the Procedural, Fault and Schedule Data Modules. The other Data Module types do not require this information.