The model is termed Arc-Node data model. Arc the basic logical entity, a series of point that starts and end at a node. Node is an intersection point where two or more arcs meet. A node can also occur at the end of a dangling arc i.e. and arc that is not connected to another arc such as the end of a dead-end street. Polygon is comprised of a closed chain of arcs that represents the boundary of the area.
Point is encoded as a single XY co-ordinate pair.
Point is considered as the polygon with no area. Model TIN is a vector-based topological data model that is used to represent terrain data. A TIN represents the terrain surface as a set of interconnected triangular facets. Z values are encoded. It lists each triangle and the nodes which define it.