Introduction Schemas defining values

Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. 239 b In an application schema modelling also feature collections, gml:AbstractFeatureMemberType and gml:AggregationAttributeGroup are required, too, as well as all schema components required by them. See Clause 7. c If the features have properties which make use of units of measure, gml:MeasureType and all specific subtypes, e.g. gml:LengthType, are required as well as all schema components required by them see Clause 8. gml:BaseUnit, gml:DerivedUnit, andor gml:ConventionalUnit and all schema components required by them, see Clause 16 are not required unless the application is defining units of measure such as appear in a units of measure dictionary. d If the application schema uses 0-dimensional spatial geometries, gml:Point is required and all schema components required by it. See Clause 10. e If the application schema uses only simple 1-dimensional spatial geometries with linear interpolation, only gml:LineString is required and all schema components required by it. See Clause 10. f If the application schema uses additional interpolation types, gml:Curve and any number of curve segments depending on the application but at least one are required. Again, this includes all schema components required by these elements. See 10.5.10. g If the application schema uses only simple 2-dimensional spatial geometries with linear interpolation along their boundaries without sharing boundary elements, only gml:Polygon and gml:LinearRing are required and all schema components required by them. See Clause 10. h If the application schema uses additional interpolation types or surface patches, gml:Surface and any number of surface patches depending on the application but at least one are required. If surfaces shall share geometric primitives along their boundaries, gml:Ring is required, too. Again, this includes all schema components required by these elements. See 10.5.10. i If the application schema uses 3-dimensional spatial geometries, gml:Solid is required and all schema components required by it. See 10.5.10. j The geometric aggregates schema components described in Clause 11 are required only, if the features use geometric objects that are collections of geometric primitives in their spatial properties. k The geometric complex and composites schema components described in Clause 11 are required only, if the features use geometric complexes in their spatial properties. l The topology schema components described in Clause 13 are required only, if the features have topology properties. m The Coordinate Reference System schema components described in Clause 12 are required only, if the application requires constructing or processing Coordinate Reference System dictionary entries and their supporting components. EXAMPLE 1 Prime Meridians, Geodetic Datums, etc. are supporting components. n The temporal schemas described in Clause 14 is required only, if the application schema is concerned with time dependent feature properties or dynamic features. o The coverage schema components described in Clause 19 are required only, if the application involves constructing or processing coverages. EXAMPLE 2 Remotely sensed images, aerial photographs, soil distribution, digital elevation models are typical coverages.