The boundary of a Polygon consists of a set of LinearRing objects (that is, LineString objects that are both simple and closed) that make up its exterior and interior boundaries.
No two rings in the boundary cross. The rings in the boundary of a Polygon may intersect at a Point, but only as a tangent.
A Polygon may not have cut lines, spikes, or punctures.
The interior of every Polygon is a connected point set.
The exterior of a Polygon with one or more holes is not connected. Each hole defines a connected component of the exterior.
In the above assertions, polygons are simple geometries. These assertions make a Polygon a simple geometry.