**4.4 Interaction process**

To focus on the suggested method for the combination of the Semantic Web technologies and the 3D processing algorithms, Fig 6 illustrates an UML sequence diagram that represents the general design of the proposed solution. Hence, the purpose is to create a more flexible, easily extended approach where algorithms will be executed reasonably and adaptively on particular situations following an interaction process.

Fig. 6. The sequence diagram of interactions between the laser scanner, the 3D processing, the knowledge processing and the knowledge base

The processing steps can be detailed where three main steps aim at detecting and identifying objects.


As intermediate steps, the different geometries within a specific 3D point clouds are detected and stored within the ontology structure. Once done, the existent topological relations between the detected geometries are qualified and then populated in the knowledge base. Finally, detected geometries are annotated semantically, based on existing knowledge's related to the geometric characteristics and topological relations, where the input ontology contains knowledge about the Deutsche Bahn railway objects and knowledge about 3D processing algorithms.
