**5.1 Class axioms**

228 Semantics – Advances in Theories and Mathematical Models

the next section. The semantic within the ontologies expressed through OWL-DL language can be used for further inferences. For instance, the following rule asserts that a Bounding Box with lines higher then 5 m are masts where Masts, Bounding Boxes and lines are all individual-valued properties. The DL syntax related to such an expression is Mast ⊑ (�������� ��� � � �������� ���� � � �as�����t� �� ��) while the swrl conversion of such an expression is BoundingBox(?x) hasLine(?x,?y) hasHeight (?y,?h) swrlb:GreaterThan

The set of built-ins for SWRL is motivated by a modular approach that will allow further extensions in future releases within taxonomy. SWRL's built-ins approach is also based on the reuse of existing built-ins in XQuery and XPath, which are themselves based on XML Schema by using the Datatypes. This system of built-ins should as well help in the interoperation of SWRL rules with other Web formalisms by providing an extensible, modular built-ins infrastructure for Semantic Web Languages, Web Services, and Web applications. Many built-ins are defined. These built-ins are keys for any external integration where we take advantages of this extensional mechanism to integrate new Built-

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

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

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

(5) From geometric and/or topological relations to semantic annotated elements.

(?h, 5) Mast(?x).

**4.4 Interaction process** 

identifying objects.

ins for 3D processing and topological processing.

the knowledge processing and the knowledge base

(3) From 3D point clouds to geometric elements. (4) From geometry to topological relations.

adaptively on particular situations following an interaction process.

The class axiom DC:DomainConcept which represents the different object found in the target scene can be considered the main class in this ontology as it is the class where the target objects are modelled, this class is further specialized into classes representing the different detected object. However, the importance of other classes cannot be ignored. They are used to either describe the object geometry through the Geom:Geometry class axiom by defining its geometric component or the bounding box of the object that indicate its coordinates or to either describe its characteristics through the Charac:Characteristics class axiom. Additionally, the suitable algorithms are automatically selected based on its compatibility within the object geometry and characteristics via the Alg:Algorithm class. Add to that, other classes, equally significant, play their roles in the backend. The connection between the basic mentioned classes is carried out through object and data properties axioms.

From Unstructured 3D Point Clouds to Structured Knowledge - A Semantics Approach 231

elements, the most useful and discriminant characteristics to detect it and their inter-

**Class Sub Class Subsub Class Height Correspondent** 

Distant Signal Between 4 and 6 m

Vorsignalbake between 1,5 and 2.5

Breakpoint\_table between 1 and 2 m

Chess\_board between 1 and 1,5 m

Table 1 shows a possible collection of scene elements in case of a Deutsche Bahn scene. They may be additionally structured in a hierarchical order as might be seen convenient for a scene while Fig8 shows the suggested taxonomical structure to model them within the OWL

Basically, a railway signal is one of the most important elements within the Deutsche Bahn scene where we find DC:main\_signals and DC:secondary\_signal. The main signals are classified onto DC:primary\_signal and DC:distant\_signal. In fact, the primary signal is a railway signal indicating whether the subsequent section of track may be driven on. A primary signal is usually announced through a distant signal. The last one indicates which image signal to be expected that will be associated to the main signal in a distance of 1 km. Actually, big variety of secondary signals exists like the DC:Vorsignalbake, the DC:Haltepunkt and others. From the other side, the other discriminant elements within the same scene are the DC:Masts presenting electricity born for the energy alimentation. Usually, masts are distant from 50 m from to others. Finally, the DC:Schaltanlage elements present small electric born connected to the ground. For detection purpose, we

m

Basic Signals Main Signal Between 4 and 6 m

**image** 

relationship is presented in Table 1 .

Secondary signal

BigMast More than 6m

NormalMast Between 5 and 6

Schalthause Less than 1m

SchaltSchrank Less than 0,5m

Table 1. Example of the Deutsche Bahn scene objects

Signals

Mast

Schaltanlage

language.

define for example a signal as:
