THE WEB SERVICES SELECTION OF VIRTUAL LEARNING ENVIRONMENT SERVICES Ajlan Al Ajlan Software Technology Research Laboratory De Montfort University The Gateway, Leicester, LE1 9BH, UK.
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Hussein Zedan Software Technology Research Laboratory De Montfort University The Gateway, Leicester, LE1 9BH, UK.
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ABSTRACT Using Internet to enhance e-learning has become a trend in modern higher education institutes. Virtual Learning Environments (VLEs) systems are increasingly becoming a significant part of the strategy for delivering online and flexible e-learning. Therefore, Web services as an example of Service Oriented Architecture (SOA) are still not generally accessible for academic institutes and will support VLEs as an integration of software applications in an incremental way, using existing platforms and languages that utilize and adopt existing legacy systems. Developers have developed VLEs services and they are continued to be adopted by some scientific projects. Nowadays, there is an increasing demand for methodologies and technologies, especially, for VLEs. Web Services Selection (WSS) involves discovering a set of semantically equivalent services by filtering a number of available services based on service metadata, and selecting an optimal service based on real-time during previous executions of a service. The spotlight of this paper is to investigate the existing approach of SOA to persuade the requirements of web applications based on e-learning systems. KEYWORDS
Service Oriented Architecture, Web Services, Web Services Selection, OSS, VLE, and MOODLE.
1. INTRODUCTION Service-Oriented Architecture has become an active area of research and development. Therefore, the ability to exchange information between internal business units, partners, and customers is essential for success. The number of several continuing research efforts focus on a variety of aspects of SOA, particular on Web services technology, including the composition, description, discovery and verification. Web services are the most promising technology of easier system integration by providing standard protocols by using Extensible Markup Language (XML) messages for data exchange and a standard interface declaration language such as the Web service description language (WSDL) [(Huhns and Singh 2005), (Mendon and Silva 2005)]. WSS involves discovering a set of semantically equivalent services by filtering a set of available services based on service metadata, and selecting a best possible service based on real-time during previous executions of a service. WSS is desirable and necessary to automate the service discovery and selection process to effectively meet user requirements and specifications. The solution for discovery and selection services should be efficient, easy, scalable, and cheap [(Huhns and Singh 2005), (Vossen and Westerkamp 2003)]. VLEs as Web Services are still not generally accessible for academic institutes. Therefore, developers have developed VLEs services and they are continued to be adopted by some scientific projects. Currently, there is an increasing demand for methodologies and technologies, especially, for VLEs. VLEs are defined as interactive learning in which the learning content is available online and provides automatic feedback to the
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student’s learning activities [(Vossen and Westerkamp 2003), ( Mecella, Ouzzani. 2006)]. VLEs offer a number of benefits, such as better integration of applications, anytime and anywhere access, improved motivation and opportunities for independent learning [(Berry 2005), (Dougiamas 2007)]. In order for current and future generations of personalized VLEs to improve educational effectiveness and efficiency, there are fundamental requirements that must be realized. While recognizing that the world at large will continue to use terminology in different and often ambiguous ways, the term of VLEs is used to refer to the online interactions of a variety of kinds, which take place between students and instructors. VLEs refer to the components between which students and teachers participate in online interactions of a variety of kinds, including online learning [(Dougiamas 2007), (Brandl 2005)]. This paper is further structured as follows. Literature review of Web services and VLE is presented in section 2. Section 3 highlights on Web services analysis. The introducing Web service to VLE (MOODLE) is described in section 4 and also this section referred to Assignment Module and PHP SOAP implementation. Finally, the discussion of this works and concludes this paper in section 5.
2. WEB SERVICES Web services are a set of emerging and established communication protocols that consist of XML, Simple Object Application Protocol (SOAP), Universal Description Discovery and Integration (UDDI) and WSDL over Hypertext Transfer Protocol (HTTP) [(Huhns and Singh 2005), (Cavanaugh 2006)]. One of the greatest advantages of Web services is their use for machine-to-machine interaction [(Yang 2003)]. Web services allow a number of applications to be integrated faster, easier and cheaper than ever before. They are expressed as a WSDL that is an XML language. A service specifies a contract between the client and the operations that it can expect. A service may be published and discovered using UDDI, while SOAP allows vendor-neutral communication among applications over HTTP [(Yang and Hsieh. 2005), (Newcomer 2002)]. Web services enable a set of pieces of software to be written in different languages and running on different operating systems in a cheap and easy way. Also, they enable a set of applications to be run in different organizations to exchange data easily and cheaply. They are applications that run anywhere on any technology or device that has a Web services. They are an automated innovation and provide a mechanism for discovering service providers, which can be automated [(Huhns and Singh 2005)]. Web services architecture is based on the interactions between three roles as in Fig. 1, [(Ambrosi and Bianchi. 2006)]: service provider, service registry and service requestor. These interactions involve publish, find and bind operations act upon the Web services artifacts. The scenario of Web services consists in four stages as below in Fig 1 and those stages are [(Huhns and Singh 2005), ( Gottschalk and Graham. 2002)]: Publish description services
Service Registry (Porker) 3 Binds invokes services
Find via UDDI
Describe via WSDL Connect via SOAP
2 Service Requester (Consumer)
Develop describe services
1 4 Bind via UDDI
Service Provider
Figure. 1: Web Services Model
1. 2. 3. 4.
Service provider is deploying and publishing the description of its services to service registry, and host these services and control access to them. Service requester works with service broker to discover the optimal services that meat and satisfy the specification of register. Service broker send the services that have been found to service requestor. Finally, service requester negotiates with service providers to bind services after they have been found.
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3. WEB SERVICES ANALYSIS The literature review is aimed at identifying the literature relevant to VLEs and SOA. Analysis and evaluate existing MOODLE and focusing on Assignment module to explore their functionalities and limitations. Moreover, An important feature of the MOODLE is the MOODLE.org web site, which provides a central point for information, discussion and collaboration among MOODLE users, who include system administrators, teachers, researchers, instructional designers and of course, developers. Deploying techniques like service descriptions, registrations, discovery and binding will open a wide door for collaborative VLE services that run under a flexible, distributed and effective manner. Moreover, it supports the world-wide trend of offering online joint courses over the internet, which includes institutes in different countries who employ roaming staff and target mobile students. In order to prove the concept we have selected a well-known service provided by a product such as VLEs (MOODLE). There are limitations for using VLEs in Saudi Universities, particularly in Qassim University, of which I am a member of staff. Some of these universities have spent a lot of money to buy VLE software and also have spent large amounts on IT experts, because VLEs software is much too difficult for normal users. The best solution regarding to this issue is that these institutes should adopt Open Source Software (OSS) such as MOODLE. OSS is almost free which means users are free to download, use, modify and even distribute it under the terms of license. The license agreement gives the licensee the right to modify and redistribute the software. The financial resources of OSS will be almost free. Currently, there are eighteen institutes that have used MOODLE in Saudi Arabia. One of them is Imam University, which has used MOODLE as a blackboard in the Computer Science Department. The higher education community increasingly sees VLEs as important tools, especially for women. In the kingdom of Saudi Arabia, there are two kinds of public educational institutions. One of them is for females and another for males. Therefore, VLEs will play an important factor in Saudi public educational institutions, especially in higher education. One of my targets is to devise and help Qassim University to adopt and bring OSS technology so that teachers can provide and share documents, graded assignments, provide quizzes, and discussion forums, etc. with students in an easy to learn and use interface. MOODLE as an example of VLEs is a fine software example of how and why OSS works. In section 4, this paper will explain in details why institutions are choosing MOODLE over others software.
4. INTRODUCING WEB SERVICES TO VLE (MOODLE) Using Web services in MOODLE allow teachers at different institutions to work together and share material by connecting individual courses together. Therefore, some educators at different institutions that teach the same course can share assignments, chat, etc and communicate with each other. MOODLE is VLEs that lets teachers provide and share documents, assignments, quizzes, etc. with their students in an easy way to learn and create quality online courses. MOODLE is free OSS which means users are free to download, use, modify and even distribute it under the terms of GNU [(Dougiamas 2007)]. Phase 1 Phase 2
VLEs ¾ C/S ¾ PHP MOODLE Abstraction
Student Teacher Guest
Module Service
Refinement
¾ C/S ¾ PHP
VLEs MOODLE
Assignment
Phase 3 Phase 4
Figure.2: The Initial Architecture for a SOC-based for VLE
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The model of this study has four phases as in Fig. 2. It will move the current MOODLE from Web application to apply Web services and these phases as follows: 1.
2.
3.
4.
Applying MOODLE that uses Client/Server application based on PHP. This phase will focus on the current MOODLE to understand its environment and explore its functionalities and limitations. Then will focus in depth on the Assignment Module which is chosen to be the specific area. The most content of objects, operations and functions in the server and client just as an interface web page passed on html. Abstraction of useful MOODLE functionalities. This phase will make abstraction to reduce and remove all data that is unnecessary from current MOODLE to retain only the information that is relevant for a particular purpose and the result is in Fig. 2. Refinement is a fundamental design technique that has often challenged the formal methods. It is the verifiable transformation of an abstract (high-level) formal specification into a concrete (low-level) executable program. Model based refinement is an important technique for ensuring efficiency, effectiveness and correctness in the practical design of complex computer based systems (SOA)????. Policy-based requests matching. Matching users’ request for services, which are available at the Service Registry. As we enable similar service to be registered simultaneously (e.g. the same course), assignment is distributed among different MOODLE servers, and matching policies allow assigning the most convenient service to the requestor. We use conceptual graphs to model the matching process.
OSS is rapidly developing, and new alternatives for nonprofits organizations are emerging and maturing. Also, OSS is becoming widely adopted by university and educational institutions. Managing an LMS can be a complex task. MOODLE does not hide this complexity and its detailed on-line help, examples and sensible defaults assist users in installing, administering and using the LMS [(Ambrosi and Bianchi. 2006)]. The study has chosen the software of MOODLE to be the area of research and analysis, because the following important reasons (Dougiamas 2007),(Chavan and Pavri 2004),(Williams 2005) (Berry 2005)]: 1. 2. 3.
MOODLE is OSS which user is free to download, use, modify and distribute it under the terms of GNU. MOODLE runs without modification on Unix, Linux, Windows, and any other system that supports PHP. Also, data is stored in MySQL, PostgreSQL, Oracle, ODBC and others. It lets teachers to provide and share documents, graded assignments, quizzes, etc. with their students in an easy way to create online courses. Also, it is a great with a range of 75 languages in 175 countries.
MOODLE is a fine example of how and why OSS works. But, it has some limitations as follows: 1. 2. 3. 4.
OSS is only for IT experts and is much too difficult for normal users to install and use. There are more than 66% users of MOODLE who identified themselves as teachers. It seems to be a difficult situation for novice technicians to install and use MOODLE, because there are many technical word lists in the community forums and installation instructions. MOODLE will work but not by itself. Forums a great deal of information, but nearly all forums are in the English.
This section is the important part of our study, because it will focus on the assignment module as a part of MOODLE to explore their functionalities and limitations. The used language for MOODLE is PHP, Therefore, the best and fastest way that we have explored is the NuSOAP package. The assignment enables teachers to allow their students to upload any digital content for grading. Students can submit articles, essays, and etc. Assignment can be set up in four assignment types as in Fig. 3. assignment_base
assignment_online assignment_uploadsingle assignment_offline assignment_upload Figure.3: The Architecture of Assignment Module in MOODLE
Currently, there is no standard API to develop SOAP applications and the most popular packages at the moment are NuSOAP, ezSOAP, and PEAR::SOAP. Our study will focus on NuSOAP packages, because: ¾ NuSOAP is a group of PHP classes that allows developers to create and consume SOAP Web services. ¾ It is a good choice to create PHP SOAP services and also does not require any special PHP extensions. ¾ It can generate WSDL and can also consume it for use in serialization [(Fuller, Fuecks. 2003)].
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5. DISCUSSION AND CONCLUSION The study is aimed at extending the core idea behind VLE (MOODLE) tools that are gradually dominating academic institutions. The contribution that we are aiming for is to build a VLE around the Web services concepts. The fundamental contribution of the proposed study is to demonstrate that the VLEs maybe considered as services which can be published, discovered and composed as perceived in a SOA paradigm. The result of this study proves that MOODLE is better than other VLE systems as the best area of study, because of the reasons that we mentioned in section 4. According to the discussion with the author and some developers of MOODLE, the assignment module has been chosen as a specific area of research. Introducing Web services to MOODLE is one of the main objects of this study. Recently, developers of MOODLE have facilitated discussion about the development of Web services. The best way to deliver Web services to MOODLE is NuSOAP. Allowing NuSOAP to dynamically generate applications can help a lot with debugging or adding new service methods, because of the reasons that we mentioned above in section 3. This paper has presented the work that has been done to date. Discovering and selecting optimal services by using existing standard technology is mostly a task of keyword-based searches in complex service descriptions. The future work of this paper is to comment on all possible problems that occur when trying to discover and select services for optimal service. The key points of this paper are to involve extended, loosely coupled activities among two or more independent academic and business partners. Such activities can be thought of as academic and business processes that engage several services in a manner that brings about the desired academic outcome. Adopting SOA has the potential to bring about decreased programming difficulty and expense, lower maintenance costs, quicker time-to-market, new revenue streams and improved operational efficiency.
ACKNOWLEDGEMENT The authors wish to acknowledge contributions from many people, including Martin Dougiamas who the author of MOODLE, Justin Filip and Martín Langhoff. We also acknowledge those with whom we have discussed issues addressed in this paper, including Al-Marghilani, Bassam zafar, and Osama El-Hassan.
REFERENCES Ambrosi, E., M. Bianchi, et al. (2006). When is it convenient to predict the web services completion time? Proceedings of the 24th IASTED international conference on Parallel and distributed computing and networks. Berry, M. G. (2005). An investigation of the effectiveness of MOODLE in primary education. Deputy Head, Haslemere. Brandl, K. (2005). "Are you Ready to "MOODLE"?" 9(2): 16-23. Cavanaugh, E. (2006). Web services: Benefits, challenges, and a unique, Altova WhitePaper. USA. Chavan, A. and S. Pavri (2004). "Open-source learning management with MOODLE." Linux Journal. Dougiamas, M. (2007). "MOODLE." from www.Moodle.org. J. Fuller, H. Fuecks, et al. (2003). Professional PHP Web Services, Wrox Press. K. Gottschalk, S. Graham. (2002). "Introduction to Web Services Architecture." IBM Systems journal 41(2): 170-177. Massimo Mecella, Mourad Ouzzani, et al. (2006). Access control enforcement for conversation-based web services. Proceedings of the 15th international conference on World Wide Web, ACM Press. Mendon, N. C. and J. A. F. Silva (2005). An empirical evaluation of client-side server selection policies for accessing replicated web services. Proceeding of the 2005 ACM symposium on Applied computing. Huhns, M. and M. Singh (2005). Service-oriented computing: Semantics, processes, agents. John Wiley and Sons Ltd. Newcomer, E. (2002). Understanding Web Services, XML/ WSOL/ SOA and UOOI, Addison-Wesley. Stefan Tai, Rania Khalaf, et al. (2004). Composition of coordinated web services. Middleware. Proceedings of the 5th ACM/IFIP/USENIX international conference on Middleware. Stephen J. H. Yang, James S. F. Hsieh, et al. (2005). Composition and evaluation of trustworthy web services. Proceedings of the IEEE EEE05 international workshop on Business services networks. Vossen, G. and P. Westerkamp (2003). "E-learning as a Web service." Wagner, M. and Balke, B. (2003)"Towards Personalized Selection of Web Services" WWW 2003(963-311-355-5) 20-24. Williams, B. (2005). "MOODLE for Teachers, Trainers and Administrators". Yang, J. (2003). "Web service componentization." ACM Press: 35–40.
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