**2.1.1 Define the scope of telecommunications service domain ontology**

The first step is mainly to define the scope and border of domain ontology. Telecommunications service domain ontology mainly addresses the semantic interoperability of telecommunications service. This domain ontology mainly provides the shared domain vocabularies and knowledge to support the semantic web applications in the telecommunication service field, such as semantic telecom service description, service discovery, and service context modelling. Therefore, TSDO should involve the servicerelated domain concepts and knowledge. For example, telecom services often involve network type, network carrier, billing policy, user terminal, service quality, service customer, service category, .etc. In fact, telecommunication service field consists of a large number of concepts/terminologies and relations. Some concepts have the higher sharing degree. However, some concepts are only related to concrete application field, such as service context ontology, service description ontology. Therefore, how to abstract the sharing domain concepts and reasonably organize them is a big challenge. The reusability and extensibility are two important ontology modeling factors considered. So an efficient ontology hierarchy modelling approach is needed.

In practice, we adopted a layered ontology modeling method to organize the domain concepts to improve the reusability and extensibility (see Figure 2). Common ontology, like time and space ontologies, can be shared in the different domains, like telecom, medical domain or any other domains. The concrete domain ontology can be shared by the different domain-related application ontologies. For example, TSDO may be used to create the service context ontology, network management ontology, etc. This method well distinguishes the border of TSDO, common ontology and telecom service-related application ontology.

Telecommunications Service Domain Ontology:

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1. **Terminal Capability Ontology**: defines main concepts about terminal software, terminal hardware, terminal browser and network characteristics supported by terminal. 2. **Network Ontology**: specifies the network concepts, network category, network features, as well as the relationships of various networks, such as mobile network,

3. **Service Role Ontology**: describes the stakeholders' concepts of the service supply chain, for example, service provider, content provider, network operator, service user. 4. **Service Category Ontology**: describes a telecommunications service classification. This ontology defines the relationship between various telecommunications services, like basic service, value-added service, voice service, data service, conference service,

5. **Charging Ontology**: defines the charging-related concepts and rules about telecommunications services, including payment methods (such as prepaid and postpaid), charging types (such as time-based, volume-based, event-based, and content-

6. **Service Quality Ontology**: A telecommunication network must provide the services which have the end-to-end QoS guarantee. Depending on the technical characteristics, the QoS provided by different networks is varying. Service Quality Ontology mainly defines the QoS-related concepts about telecommunications service, including access network QoS, core network QoS and user's QoE, such as call delay, message size, call

**2.1.3 Multi-channel acquisitions of telecom service-related domain concepts and** 

After the framework of TSDO is set up, it needs to collect domain concepts and knowledge (including terminologies and their relationships) from multi-channel ways for each subontology of TSDO. In general, the sources of knowledge acquisition include the released telecom service specifications, senior experts in the telecom field or some typical application

internet, and fixed network, GSM, CDMA, UMTS, WCDMA, and WLAN.

presence service, download service, browsing service, messaging service.

based), billing rates, as well as account balances.

**knowledge** 

through rate, positioning accuracy, network bandwidth.

Fig. 4. Some collected domain concepts about telecom network.

Fig. 2. Layered ontology modelling method.

#### **2.1.2 Set the framework of telecommunications service domain ontology**

When the goal and scope of TSDO are clear, the specific organization framework of TSDO should be set up. As TSDO involves a large number of telecom service domain concepts and relationships, how to reasonably classify and organize these terminologies is an important issue. Specifically, we adopted a modular modelling approach to construct TSDO. The principle of modular modelling is the "strong cohesion and loose coupling" way. The correlations among different concepts are the main reference of module division. The goal of modular modelling is to ensure that the correlation of concepts in the same module is stronger. Based on this modular design principle, TSDO is divided into several subontologies as shown in Fig. 3.

Fig. 3. The framework of telecommunications service domain ontology.

Specifically, TSDO mainly comprises six sub-ontologies, including Terminal Capability Ontology, Network Ontology, Service Role Ontology, Charging Ontology, Service Quality Ontology, and Service Category Ontology.

Fig. 2. Layered ontology modelling method.

ontologies as shown in Fig. 3.

**2.1.2 Set the framework of telecommunications service domain ontology** 

Fig. 3. The framework of telecommunications service domain ontology.

Ontology, and Service Category Ontology.

Specifically, TSDO mainly comprises six sub-ontologies, including Terminal Capability Ontology, Network Ontology, Service Role Ontology, Charging Ontology, Service Quality

When the goal and scope of TSDO are clear, the specific organization framework of TSDO should be set up. As TSDO involves a large number of telecom service domain concepts and relationships, how to reasonably classify and organize these terminologies is an important issue. Specifically, we adopted a modular modelling approach to construct TSDO. The principle of modular modelling is the "strong cohesion and loose coupling" way. The correlations among different concepts are the main reference of module division. The goal of modular modelling is to ensure that the correlation of concepts in the same module is stronger. Based on this modular design principle, TSDO is divided into several sub-


### **2.1.3 Multi-channel acquisitions of telecom service-related domain concepts and knowledge**

After the framework of TSDO is set up, it needs to collect domain concepts and knowledge (including terminologies and their relationships) from multi-channel ways for each subontology of TSDO. In general, the sources of knowledge acquisition include the released telecom service specifications, senior experts in the telecom field or some typical application

Fig. 4. Some collected domain concepts about telecom network.

Telecommunications Service Domain Ontology:

Fig. 6. Part of network ontology formalized by OWL.

**2.1.6 Evaluation of telecommunications service domain ontology** 

Ontology evaluation is an important issue that must be addressed if TSDO are to be widely adopted in the semantic related telecommunications applications. Ontology can be

"MobileNetwork".

**ontology** 

concepts.

Semantic Interoperation Foundation of Intelligent Integrated Services 189

Figure 5 shows the conceptual model of network ontology in part. Based on the terminologies collected in the above step, the class hierarchy and relationships are described. This conceptual model depicts the classification of network, the services provided by network and the operator of network. It can be seen that the ranges of object property "operatedBy" and "provides" are the concepts from ServiceRole and ServiceCategory subontologies respectively. In addition, we define the domain axioms through the constraints way. For example, we define that "FixedNetwork" is disjointed with "MobileNetwork", i.e. if N1 is an instance of concept "FixedNetwork", then it will not be an instance of concept

**2.1.5 Formalization of conceptual model of telecommunications service domain** 

As the conceptual model is one high-level abstract model and independent of any concrete ontology modelling languages, we need to formalize this conceptual model through a specific ontology modelling language like OWL (Web Ontology Language) (W3C, 2004a). In general, we can use the common ontology modelling tools to formally describe the terminologies, relationships and axioms in the conceptual model. Figure 6 shows the formalization description of part concepts and relationships of Figure 5 by OWL language. The concept is formally defined by "owl:Class", and the class hierarchy is organized by "owl:subClassOf". The "owl:ObjectProperty" is used to describe the relationships between the concepts and the "owl:disjointWith" clearly depicts the restrictions on the two disjointed

scenarios. In this step, modellers need to list the collected concepts, relations and explanations as far as possible. It's unnecessary to care about the meaning overlap between the concepts and to consider how to express these concepts and their relation in class, property or instance ways. For example, Figure 4 briefly shows the concepts collection about network ontology.
