**2.2.3 PIM step: Terminology acquisitions and conceptual modeling of TSDO**

After defining the CIM of TSDO, the following step is to construct the PIM of TSDO. It means that the telecom service related domain terminologies should be collected and then integrated into a high-level abstract domain ontology model which is independent of a specific ontology language like OWL. The collection of domain terminologies can be modeled by the UML Use Case diagram like Figure 4. However, the high-level domain conceptual modeling is the emphasis of PIM. How to model the conceptual model of domain ontology based on UML is needed to resolve. Fortunately, UML and ontology language have some common features, although sometimes represented differently. This provides a possible transformation from UML model to ontology model. For example, both ontology representation language and UML are based on *Class*. The *Generalization* elements of UML can represent the subClass or subProperty semantic of ontology. The ownedAttribute of UML Class can describe the DatatypeProperty of ontology language. The mapping example is illustrated in the Figure 12.

Fig. 12. The direct mapping example from UML to OWL.

However, although UML Class diagram has some constructs similar to the constructs of ontology representation language, there are still some ontology constructs which cannot be represented by UML constructs directly. We need to find the appropriate UML elements to represent some other ontology constructs, like objectProperty, equivalent class relation, and disjointing class relation. For instance, we can select the directedAssociation element of UML to represent the ObjectProperty and use the constraints anchored with association to represent the inverse, symmetric or transitive feature of ObjectProperty. An illustrated example is shown in Figure 13.

As a common software modeling language, most of software developers, system analysts and designers are familiar with UML. So, in order to decrease the technical threshold, it's a practical approach for the conceptual modeling of TSDO by UML. Although UML has some similar constructs with ontology language, however, the modeling goals and description capabilities of both languages have some differences. From the above analysis, in order to use UML to represent high-level ontology conceptual model, we need to define a specific tailored representation method to guide the modeler to build the conceptual model of domain ontology. Table 1 shows the main corresponding relation of UML elements with ontology elements. According to this semantic representation way, the modeler can use the UML elements to describe the semantic-enabled high-level ontology conceptual model like Figure 14.

Telecommunications Service Domain Ontology:

to complete the model transformation.

Source MetaModel

Instantiation

Fig. 15. The principle of model transformation.

Semantic Interoperation Foundation of Intelligent Integrated Services 197

It can be seen that the high-level ontology conceptual model described by UML is independent of a specific ontology language. So, in order to generate the formal file encoded by a specific ontology language, we need to transform the PIM into PSM according to the concrete model transformation rules. Figure 15 shows the general model transformation mechanism of model driven architecture. Model transformation is essentially to map the source model elements to other elements of the target model. Models are usually the instantiation of its meta-model. The model transformation rules are generally defined in the metamodel level and then model transformation engine apply these rules to the model level

> Definition of Transformation Rules

Model Transformation Engine

Target Model Source Model

Application of Transformation Rules

Therefore, in order to transform the high-level ontology conceptual model (i.e. PIM) into platform specific model (i.e. PSM), we need to define the transformation rules according to the source and target metamodels. In our proposed approach, the high-level ontology conceptual model (i.e. PIM) is modeled by UML2.0, and the source metamodel is UML2.0 metamodel obviously. So we need a target metamodel relating to specific ontology language to describe the formal ontology model (i.e. PSM). In fact, OMG (Object Management Organization), which is the promoter of MDA, has considered this problem. In May 2009, OMG released the Ontology Definition Metamodel (ODM) v1.0 (OMG, 2009) based on the

Instantiation

Target MetaModel

Fig. 14. PIM: A part of high-level conceptual model of network ontology.

**2.2.4 PIM to PSM step: Formalization of ontology conceptual model** 

Fig. 13. The indirect mapping example from UML to OWL.


Table 1. The defined UML representation method for high-level conceptual model of domain ontology.

(a) (b)

**UML Elements Ontology Elements Comments** 

maxCardinality

Inverse Symmetric Transitive Functional

equivalentClass

Table 1. The defined UML representation method for high-level conceptual model of

ontology cardinality declared only for range

The value of "owned By" property of Association End A is the domain of ObjectProperty, the value of "owned By" property of Association End B is the range of ObjectProperty.

Fig. 13. The indirect mapping example from UML to OWL.

Class Class

Generalization subClass, subProperty Instance Individual

Multiplicity minCardinality

ownedAttribute Datatype Property

directedAssociation ObjectProperty

Enumeration oneOf

Association Class disjointWith

Constraint

domain ontology.

Fig. 14. PIM: A part of high-level conceptual model of network ontology.
