12.18.2. The OpenGIS Geometry Model

12.18.2.1. The Geometry Class Hierarchy
12.18.2.2. Class Geometry
12.18.2.3. Class Point
12.18.2.4. Class Curve
12.18.2.5. Class LineString
12.18.2.6. Class Surface
12.18.2.7. Class Polygon
12.18.2.8. Class GeometryCollection
12.18.2.9. Class MultiPoint
12.18.2.10. Class MultiCurve
12.18.2.11. Class MultiLineString
12.18.2.12. Class MultiSurface
12.18.2.13. Class MultiPolygon

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.