If arcDescription.type is circularArc or ellipticalArc, then pointList must contain exactly two points.
Arc is the locus of points connecting a list of points. Every arc must include at least two points in the point list defining position, as well as a description which defines the mathematical method used for generating the locus.
If the arc is a circular arc or an elliptical arc (as indicated under description), position must be defined as consisting of exactly two points. The order of the two points is such that a clockwise direction, from the first point to the second point around the circle or ellipse, specifies the arc. If a complete circle or ellipse is intended, the same point is repeated in the list of points defining position.
If the description is unspecified, the points on the arc are assumed to be connected by straight lines; that is, the choice of arc (from CurveChoice) as specified in the arc description is assumed to be line.