2.1.6 LineString, Line, LinearRing
A LineString is a Curve with linear interpolation between points. Each consecutive pair of points defines a line segment.
A Line is a LineString with exactly 2 points.
A LinearRing is a LineString that is both closed and simple. The curve in Figure 2.2—(3) is a closed LineString that is a LinearRing. The curve in Figure 2.2—(4) is a closed LineString that is not a LinearRing.