Data are distributed in some sort of coordinate space index ed by one or more dimension al variables, each of which varies independently of the others. This implies the use of a general data array as our basic model of how data are accessed, with the proviso that irregularly distributed data must also be accommodated. These indices , along with those which select component s from a datum , tend to fall into a few functional groups, which we refer to as dimensional levels . We designate indices which select component s within a datum as Level 0 dimensions. The coordinate s of a datum comprise the Level 1 and Level 2 dimensions of the data.
Data are most likely to be stored in groups, or records.
Level 2 dimensions are those coordinate s that vary across records. They are considered to vary across groups of data and may be unbounded. Carrying the above example forward, each wind measurement will have a location in longitude, latitude, pressure, and time associated with it. The two dimension s, latitude and longitude, would then belong to Level 1 . The other coordinate s, pressure and time, would index these latitude-longitude arrays, and would therefore belong to Level 2 .