The ring is closed, such that the first and last referenced points are equal or identical (i.e, shared).
A Ring consists of one or more contiguous arcs such that the initially referenced point in the first arc and the last referenced point in the last arc coincide to form a closed structure. No component arc in the ring structure may intersect, or cross, itself or another arc in the ring. The ring may be organized in either a clockwise or counterclockwise direction.