The default Dcel class used by the Arrangement_2 class-template is parameterized by a traits class, which is a model of the ArrangementBasicTraits_2 concept. It simply uses the nested Traits::Point_2 and Traits::X_monotone_curve_2 to instantiate the base vertex and halfedge types, respectively. Thus, the default Dcel records store no other information, except for the topological incidence relations and the geometric data attached to vertices and edges.
#include <CGAL/Arr_default_dcel.h>
Arr_dcel_base< | Arr_vertex_base<typename Traits_::Point_2>, |
Arr_halfedge_base<typename Traits_::X_monotone_curve_2>, | |
Arr_face_base> |