Points and polygons are represented in this example.
Ordered points can belong to polygons. A single
point and a set of points representing
a polygon can be moved. There are also colored
points.

Polygon.use:
three classes Point, ColorPoint (subclass of Point) and
Polygon
one association (with stereotype ordered)
Polygon_Point between points and polygons
for each class, there is an operation
with side effects for moving the points resp.
polygons and the corresponding constraints
(postconditions) defined

Polygon.cmd:
creates a polygon and three points
one of it is colored
then the polygon, a point and the colored point
are moved