Name	Data Type	Definition
upperLimit	ValDistanceVerticalType	Upper limit of the block. The data type also allows a special non-numerical value "CEILING", meaning "the top of the airspace. This can useful in the case of Airspace that have a non-constant upper limit.
upperLimitReference	CodeVerticalReferenceType	A code indicating the reference for a vertical distance. Two series of values exist: 1) real distance: from GND, from the MSL, from the WGS-84 ellipsoid 2) pressure distance: QFE, QNH, STD.
lowerLimit	ValDistanceVerticalType	Lower limit of the block. The data type also allows a special non-numerical value "FLOOR" meaning "the bottom of the airspace". This can useful in the case of Airspace that have a non-constant lower limit.
lowerLimitReference	CodeVerticalReferenceType	A code indicating the reference for a vertical distance. Two series of values exist: 1) real distance: from GND, from the MSL, from the WGS-84 ellipsoid 2) pressure distance: QFE, QNH, STD.
altitudeInterpretation	CodeAltitudeUseType	Indicates how the upper and/or lower altitude values should be interpreted.

Association	Multiplicity	Role	To	Role description
isRestrictedTo	0..1	discreteLevelSeries	StandardLevelColumn	Restriction of the AirspaceLayer to a number of standard IFR or VFR levels.
hasAnnotations	0..*	annotation	Note

From	Association	Multiplicity	Role	To	Role description
AirspaceActivation	concerns	0..*	levels	The level and time associated with the airspace usage part.
AirspaceLayerClass	concerns	0..*	associatedLevels	The levels and times associated with the airspace class.
RouteAvailability	concerns	0..*	levels	The level and time block referenced by the usage.
AerialRefuellingTrack	concerns	0..*	verticalExtent	The vertical extent of the AerialRefuellingTrack.
AerialRefuellingAnchor	concerns	0..*	verticalExtent	The vertical extent of the AerialRefuellingAnchor.

1 - Aerial Refuelling , 1- Standard Levels , 2 - Aerial Refuelling Availability , 3 - Airspace Classification , 4 - Airspace Activation , 4 - Route Availability