Lecture Notes in Computer Science- P93 pps

An E-Learning System Engineering Ontology Model on the Semantic Web 449 2) Services registration Module: The module stores the information of the specific services agent systems including their credit evaluation records. When the system adds some new services, the information of those services should be published to the registration information database through credit evaluation / service module. 3) Order Module: The module addresses the implementation of orders and transmits the results to the heterogeneous systems in a unified RDF form to the Web servers. 2.3 Agent System Layer Agent systems layer provides a variety of logistics services. There are a lot of differ- ences in the data forms due to the difference of the size and type of the E-learning system, collection and requirements of data. These data has still significant difference whether in the description or in storage, therefore, information center and converter should be constructed for various services agency. E-learning system converter can convert the services submitted by the services parser into a variety of operations for different services, and hand them for the order actuator to implement their services by accessing the data dictionary in the information center. Similarly, when a new agency joins the E-learning system, its service information should be transformed and stored in the information center. At the same time, its integrity and the basic conditions will be stored in the registration information database to be accessed by users online. 3 Ontology and E-Learning System 3.1 Ontology Ontology is the study of existence of all kinds of entities (abstract and concrete) that make up the world. Ontology defines the kinds of things that exist in the application domain. Without ontology, the terms and symbols of a domain will be ill-defined and confusing [10], [11]. Ontology, therefore, is a content theory about the sorts of ob- jects, properties of objects, and relations between objects in a specified domain [12]. It is a representation vocabulary specializing in a domain and includes terms that capture the conceptualizations of the domain elements. A conceptualization is an abstract, simplified view of the world that we wish to represent for some purpose [13]. The subject of ontology is the study of the categories of things that exist or may exist in some domain. On the Web, the use of Ontology needs the support of language Web in order to promote interoperability and make full use of existing tools. In order to enable Web Ontology data can be widely understood and accepted, a clear set of terms must be defined on the Web in the name space so as to provided consistent understanding of the semantics for the data described by the ontology. Ontology describes resources, but also describes services [13]. For example, Web services based on OWL ontology can be used to support Web services, through sign language to provide a core constructed set to describe the functions and attributes of Web services in a computer understandable form. OWL-S's goal is to promote the automation of Web services, including automated Web services such as synthesis and interoperability. 450 W. Tan et al. 3.2 Semantic Ontology Mapping Model Semantic Ontology mapping is used to describe the semantic relationships between the concepts. The semantic exchange and reservations of information between the two E-learning applications need to build a logic mapping mechanism for the similar con- cept in each application [14]. Therefore, semantic integration is equivalent to building a correct mapping relationship between the two E-learning systems, which provide a means of communication in the mapping implementation. Semantic Mapping is a very effective visualization technology in the E-learning process description [15]. In the paper, we designed a semantic mapping model based on goals, task, and property to describe the mapping of process and organization, the process model and the coor- dination, and the learning activities and related resources. The education service model is mapped to the application system model based on the concept of peer- related, partial-overall, and includes-ownership shown in Figure 2. S i mp l e Methods A ddi t i ona l Actions Met h o d Combination A ll S i nge Methods Ontologies Final Mappings Similarity Multiple rounds Fig. 2. Ontology mapping model This process deals with the mapping of different data descriptions in the ware- house. For example, data source formats are usually mapped to the attributes of the staging tables. 4 Communication Module Based on SOAP and ONTOLOGY In this module, we design a common client terminal, which can automatically gen- erate one or more the corresponding client agent objects to access the services in the server through the URL of the ontology documents inputted by user (obtained through the above modules), or the address of the local disk location, or analytical ontology text of the ontology string directly inputted by user. The function of the module is that whatever services is provide by the server, as long as service user give out ontology documents, the model should be able to automatically generate the corresponding request to access the different services that provided by different subsystems crossed the heterogeneous systems. Meanwhile, we had done an expan- sion that an encryption and decryption model is embedded for the information of the server and client communication in the application layer of the model, in order An E-Learning System Engineering Ontology Model on the Semantic Web 451 Learning ClassInstruction Instructor Use Communication UserInfoMassage use Learner LearningPlanning Mas sager Fig. 3. A segment of use case to ensure information security. The learners of the system own mainly operations that are learning, user information management, communication with each other and learning planning. The use case figure is shown in Fig. 3. Meanwhile, the instructors of every course take charge of the consultations of the learners, and answer their question online. The consultations have got together to the : Learner Learning Task1 Learning Task2 Learning Task3 Learning Task4 1: inputTask'sInfo 2: click"AddTask"button 3: AddTask(taskInfo) 4: New(TaskInfo) 5: add a item into Listbox 9: re-back 7: re-back 6: New(TaskInfo) 8: re-back Fig. 4. Sequence diagram of learning activation 452 W. Tan et al. class instruction model to the course instructor. The duty of the manager is update the learning source, manage the communication personal information of learners. In the Fig. 3, the work flow model is showed of the learning activation. After the login, the learner inputs the information of the learning task to do the first learning task, then, clicks the Add Task button to start the second learning task. If the second task is unready, the work flow re-backs to the first task. The module is designed to dynamically generate client agents to communicate with the corresponding services in the server based on analytic ontology documents, which is the key idea of the module [16, 17]. Meanwhile, there is another one that an encryp- tion and decryption expansion model is implemented by SOAP in application layer. Namely, sensitive information Packaged in the SOAP body is achieved encryption through the SOAP extension technology. The encrypted information is transmitted in the network. And then the decryption or other treatments are implemented respec- tively in the client terminal and server. The general process of the communication in the client and server is as follows. 5 A Case Study Based on the communication model designed in above paragraphs, we implemented a program of the core issues, which includes a services discovery module, a registration module, and a communication module based on SOAP and ontology. Meanwhile, the three modules were tested and evaluated in our laboratory. The implementation of the communication model is achieved on the .NET development platform and in the C# language both provided by Microsoft. Following the design of the section 4, the paper gives out the timing plan diagram that is shown in Fig. 5. : Learner LearningTask1 LearningTask2 LearningTask3 LearningTask4 inputTask'sInfo click"AddTask"button AddTask(taskInfo) New(TaskInfo) add a item into Listbox New(TaskInfo) re-back re-back re-back Fig. 5. Timing plan diagram of learning activation An E-Learning System Engineering Ontology Model on the Semantic Web 453 5.1 UDDI-Based Service Discovery Module As a complete communications model, first of all, needs for the existing Web service discovery and positioning[17], finds the corresponding ontology files, thus further analyses ontology documents, to the structure corresponding SOAP message to achieve communications. Therefore, we firstly designed the discovery service model. Require Services Release Services Communication Using SOAP UDDI Registration Centre Provided by Microsoft or IBM User Terminal Server Fig. 6. Principle of service discovery model Fig. 7. Class relation of learning activation . LearningTask3 LearningTask4 inputTask'sInfo click"AddTask"button AddTask(taskInfo) New(TaskInfo) add a item into Listbox New(TaskInfo) re-back re-back re-back Fig. 5. Timing plan. by accessing the data dictionary in the information center. Similarly, when a new agency joins the E-learning system, its service information should be transformed and stored in the information. communication in the mapping implementation. Semantic Mapping is a very effective visualization technology in the E-learning process description [15]. In the paper, we designed a semantic mapping model