Oracle 5.0 Reference Manual page 998

•
GeometryCollection
•
MultiPoint
•
MultiCurve
•
MultiLineString
•
MultiSurface
•
MultiPolygon
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).
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
• represents zero-dimensional objects.
Point
• represents one-dimensional objects, and has subclass LineString, with sub-subclasses
Curve
and LinearRing.
Line
•
Surface
•
GeometryCollection
MultiPoint, MultiLineString, and
to collections of Points, LineStrings, and Polygons, respectively.
MultiSurface
handle
Curves
Geometry, Curve, Surface, MultiCurve, and
classes. They define a common set of methods for their subclasses and are included for extensibility.
Point, LineString, Polygon, GeometryCollection, MultiPoint, MultiLineString, and
MultiPolygon
12.16.2.2. Class
Geometry
is the root class of the hierarchy. It is a noninstantiable class but has a number of properties
Geometry
that are common to all geometry values created from any of the
properties are described in the following list. Particular subclasses have their own specific properties,
described later.
Geometry Properties
A geometry value has the following properties:
• Its type. Each geometry belongs to one of the instantiable classes in the hierarchy.
• Its SRID, or Spatial Reference Identifier. This value identifies the geometry's associated Spatial
Reference System that describes the coordinate space in which the geometry object is defined.
In MySQL, the SRID value is just an integer associated with the geometry value. All calculations are
done assuming Euclidean (planar) geometry.
The OpenGIS Geometry Model
(instantiable)
(instantiable)
(noninstantiable)
(instantiable)
(noninstantiable)
(instantiable)
class has subclasses for Point, Curve, Surface, and GeometryCollection:
is designed for two-dimensional objects and has subclass Polygon.
has specialized zero-, one-, and two-dimensional collection classes named
are introduced as abstract superclasses that generalize the collection interfaces to
and Surfaces.
are instantiable classes.
for modeling geometries corresponding
MultiPolygon
MultiSurface
Geometry
978
Geometry
and
MultiCurve
are defined as noninstantiable
subclasses. These