MySQL 5.6 Reference Manual Including MySQL NDB Cluster 7.3-7.4 Reference Guide
The geometry classes define a hierarchy as follows:
Geometry
(noninstantiable)
Point
(instantiable)
Curve
(noninstantiable)
LineString
(instantiable)
Line
LinearRing
Surface
(noninstantiable)
Polygon
(instantiable)
GeometryCollection
(instantiable)
MultiPoint
(instantiable)
MultiCurve
(noninstantiable)
MultiLineString
(instantiable)
MultiSurface
(noninstantiable)
MultiPolygon
(instantiable)
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).
The base Geometry
class has subclasses for
Point
, Curve
,
Surface
, and
GeometryCollection
:
Point
represents zero-dimensional
objects.
Curve
represents one-dimensional
objects, and has subclass LineString
,
with sub-subclasses Line
and
LinearRing
.
Surface
is designed for two-dimensional
objects and has subclass Polygon
.
GeometryCollection
has specialized
zero-, one-, and two-dimensional collection classes named
MultiPoint
,
MultiLineString
, and
MultiPolygon
for modeling geometries
corresponding to collections of Points
,
LineStrings
, and
Polygons
, respectively.
MultiCurve
and
MultiSurface
are introduced as abstract
superclasses that generalize the collection interfaces to
handle Curves
and
Surfaces
.
Geometry
, Curve
,
Surface
, MultiCurve
, and
MultiSurface
are defined as noninstantiable
classes. They define a common set of methods for their
subclasses and are included for extensibility.
Point
, LineString
,
Polygon
,
GeometryCollection
,
MultiPoint
,
MultiLineString
, and
MultiPolygon
are instantiable classes.