The geometry classes define a hierarchy as follows:
It is not possible to create objects in noninstantiable classes. It is possible to create objects in instantiable classes. All classes have properties, and instantiable classes may also have assertions (rules that define valid class instances).
Geometry is the base class. It is an
abstract class. The instantiable subclasses of
Geometry are restricted to zero-, one-, and
two-dimensional geometric objects that exist in
two-dimensional coordinate space. All instantiable geometry
classes are defined so that valid instances of a geometry
class are topologically closed (that is, all defined
geometries include their boundary).
Geometry class has subclasses for
Pointrepresents zero-dimensional objects.
Curverepresents one-dimensional objects, and has subclass
LineString, with sub-subclasses
Surfaceis designed for two-dimensional objects and has subclass
GeometryCollectionhas specialized zero-, one-, and two-dimensional collection classes named
MultiPolygonfor modeling geometries corresponding to collections of
MultiSurfaceare introduced as abstract superclasses that generalize the collection interfaces to handle
MultiSurface are defined as noninstantiable
classes. They define a common set of methods for their
subclasses and are included for extensibility.
MultiPolygon are instantiable classes.