Intersection table representing the resolution of a many to many relationship.

vertex_s (FSK, M: CHAR VARYING(19))
vertex_t (M: CHAR VARYING(16))
edge_s (FSK, M: CHAR VARYING(19))
edge_t (M: CHAR VARYING(16))

edge.vertex
Defines the zero, one or two vertices which form the boundary of the edge.
line_element.vertex
Specifies the pair of point elements which delimit this line.
vertex.edge
Defines the edges for which this vertex forms part of the boundary.
vertex_s: Implements a foreign key to a row in one of the tables projected from entity vertex depending on the value of the next column (See below).
vertex_t: Defines the name of the referenced table. Possible values are defined in @vertex.
edge_s: Implements a foreign key to a row in one of the tables projected from entity edge depending on the value of the next column (See below).
edge_t: Defines the name of the referenced table. Possible values are defined in @edge.