**5. Description of the WiDOP knowledge base**

This section discusses the different aspects related to the domain concept top level ontology structure installed behind the WiDOP Deutsche Bahn prototype (Ben Hmida, et al., 2010). It´s composed mainly by the classes and their relationships. Hence, we try to discuss theses component in term of axiom representing them.

The domain ontology presents the core of our research and provides a knowledge base to the created application. The global schema of the modelled ontology structure offers a suitable framework to characterize the different Deutsche Bahn elements from the 3D processing point of view. The created ontology is used basically for two purposes:


In fact, the ontology is managed through different components of description logics where the class axioms contain their own prefixes used to define their names. One of the big advantages of using prefix is that the same class could be used by applying different prefix for the class. Other advantages include the simplification in defining the resource and to solve the ambiguity for different context. The hierarchical structure of the top level class axioms of the ontology is given in Fig 7, where we find five main classes within other data and objects properties able to characterize the scene in question.
