In one approach to anomaly detection, objects are represented as points in a multidimensional space, and the points are grouped into successive shells, where each shell represents a layer around a grouping of points, such as a convex hull. An object is an anomaly if it lies in one of the outer shells.
(a) To which of the definitions of an anomaly in Section 10.1.2 is this definition most closely related?
(b) Name two problems with this definition of an anomaly.