The Relief module supports representation of the terrain. CityGML supports terrain representations at different levels of detail, reflecting different accuracies or resolutions. Terrain may be specified as a regular raster or grid, as a TIN, by break lines, and/or by mass points. ADEOfAbstractReliefComponent acts as a hook to define properties within an ADE that are to be added to AbstractReliefComponent. ADEOfBreaklineRelief acts as a hook to define properties within an ADE that are to be added to a BreaklineRelief. ADEOfMassPointRelief acts as a hook to define properties within an ADE that are to be added to a MassPointRelief. ADEOfRasterRelief acts as a hook to define properties within an ADE that are to be added to a RasterRelief. ADEOfReliefFeature acts as a hook to define properties within an ADE that are to be added to a ReliefFeature. ADEOfTINRelief acts as a hook to define properties within an ADE that are to be added to a TINRelief. An AbstractReliefComponent represents an element of the terrain surface - either a TIN, a raster or grid, mass points or break lines. Indicates the Level of Detail of the terrain component. Indicates the geometrical extent of the terrain component. The geometrical extent is provided as a 2D Surface geometry. Augments AbstractReliefComponent with properties defined in an ADE. A BreaklineRelief represents a terrain component with 3D lines. These lines denote break lines or ridge/valley lines. Relates to the 3D MultiCurve geometry of the MassPointRelief. This association role is used to represent ridge or valley lines. Relates to the 3D MultiCurve geometry of the MassPointRelief. This association role is used to represent break lines. Augments the BreaklineRelief with properties defined in an ADE. A MassPointRelief represents a terrain component as a collection of 3D points. Relates to the 3D MultiPoint geometry of the MassPointRelief. Relates to the 3D PointCloud of the MassPointRelief. Augments the MassPointRelief with properties defined in an ADE. A RasterRelief represents a terrain component as a regular raster or grid. Relates to the DiscreteGridPointCoverage of the RasterRelief. Augments the RasterRelief with properties defined in an ADE. A ReliefFeature is a collection of terrain components representing the Earth's surface, also known as the Digital Terrain Model. Indicates the Level of Detail of the ReliefFeature. Relates to the terrain components that are part of the ReliefFeature. Augments the ReliefFeature with properties defined in an ADE. A TINRelief represents a terrain component as a triangulated irregular network. Relates to the triangulated surface of the TINRelief. Augments the TINRelief with properties defined in an ADE.