11.4.2 The OpenGIS Geometry Model

11.4.2.1 The Geometry Class Hierarchy
11.4.2.2 Geometry Class
11.4.2.3 Point Class
11.4.2.4 Curve Class
11.4.2.5 LineString Class
11.4.2.6 Surface Class
11.4.2.7 Polygon Class
11.4.2.8 GeometryCollection Class
11.4.2.9 MultiPoint Class
11.4.2.10 MultiCurve Class
11.4.2.11 MultiLineString Class
11.4.2.12 MultiSurface Class
11.4.2.13 MultiPolygon Class

The set of geometry types proposed by OGC's SQL with Geometry Types environment is based on the OpenGIS Geometry Model. In this model, each geometric object has the following general properties:

It is associated with a spatial reference system, which describes the coordinate space in which the object is defined.
It belongs to some geometry class.