Oracle 5.0, Справочное руководство

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The OpenGIS Geometry Model
982
• A
MultiCurve
is simple if and only if all of its elements are simple; the only intersections between
any two elements occur at points that are on the boundaries of both elements.
• A
MultiCurve
boundary is obtained by applying the “mod 2 union rule” (also known as the “odd-
even rule”): A point is in the boundary of a
MultiCurve
if it is in the boundaries of an odd number of
MultiCurve
elements.
• A
MultiCurve
is closed if all of its elements are closed.
• The boundary of a closed
MultiCurve
is always empty.
12.16.2.11. Class
MultiLineString
A
MultiLineString
is a
MultiCurve
geometry collection composed of
LineString
elements.
MultiLineString
Examples
• On a region map, a
MultiLineString
could represent a river system or a highway system.
12.16.2.12. Class
MultiSurface
A
MultiSurface
is a geometry collection composed of surface elements.
MultiSurface
is a
noninstantiable class. Its only instantiable subclass is
MultiPolygon
.
MultiSurface
Assertions
• Two
MultiSurface
surfaces have no interiors that intersect.
• Two
MultiSurface
elements have boundaries that intersect at most at a finite number of points.
12.16.2.13. Class
MultiPolygon
A
MultiPolygon
is a
MultiSurface
object composed of
Polygon
elements.
MultiPolygon
Examples
• On a region map, a
MultiPolygon
could represent a system of lakes.
MultiPolygon
Assertions
• A
MultiPolygon
has no two
Polygon
elements with interiors that intersect.
• A
MultiPolygon
has no two
Polygon
elements that cross (crossing is also forbidden by the
previous assertion), or that touch at an infinite number of points.
• A
MultiPolygon
may not have cut lines, spikes, or punctures. A
MultiPolygon
is a regular,
closed point set.
• A
MultiPolygon
that has more than one
Polygon
has an interior that is not connected. The
number of connected components of the interior of a
MultiPolygon
is equal to the number of
Polygon
values in the
MultiPolygon
.
MultiPolygon
Properties
• A
MultiPolygon
is a two-dimensional geometry.
• A
MultiPolygon
boundary is a set of closed curves (
LineString
values) corresponding to the
boundaries of its
Polygon
elements.
• Each
Curve
in the boundary of the
MultiPolygon
is in the boundary of exactly one
Polygon
element.
• Every
Curve
in the boundary of an
Polygon
element is in the boundary of the
MultiPolygon
.