An Object Oriented model uses functions to model spatial and non-spatial relationships of geographic objects and the attributes.

An object is an encapsulated unit which is characterized by attributes, a set of orientations and rules.

An object oriented model has the following characteristics.

generic properties : there should be an inheritance relationship.
abtraction : objects, classes and super classes are to be generated by classification, generalization, association and aggregation.
adhoc queries : users can order spatial operations to obtain spatial relationships of geographic objects using a special language.

For example, let us try to represent a thought : "Hawaii is an island that is a state of USA" in GIS. In this case, we don’t mind the geographic location with latitude and longtitude in the conventional GIS model. This is not appropriate to use the layers. In an object oriented model, we are more careful with spatial relationships for example, "is a" (island is a land) and "part of" (state is a part of country). In addition Hawii (state) has Honolulu City and also is in Pacific Region. Figure 4.5 (a) shows "is a" inheritance for the super class of land, while Figure 4.5 (b) shows the spatial relationships for the object of state.

An object oriented database is based on a semantic model as shown in Figure 4.6, which is usually manged by a spacial language although the language has not yet been fully completed.