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Jurnal an implementable architecture of an e-learning system

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  • 1. -001-AN IMPLEMENTABLE ARCHITECTURE OF AN E-LEARNING SYSTEMXiaofei Liu, Abdulmotaleb El Saddik and Nicolas D. GeorganasDistributed and Collaborative Virtual Environments Research LabSchool of Information Technology and EngineeringUniversity of OttawaOttawa, Ontario, Canada{xiaofei, abed, georganas}@discover.uottawa.caAbstractThis paper analyses current standards and proposalsfor e-learning system architecture. Its main objective is tocontribute an original proposal for a functionalarchitecture and service architecture for buildingstandard-driven distributed and interoperable learningsystems. The functional architecture defines componentsthat make up an e-learning system and the objects thatmust be moved among these components.We implement the service model with Web Servicestechnology to provide a standard means of communicationamong different Learning management systems anddifferent content authoring tools. This paper focuses onhow to integrate Web Services on the e-learningapplication domain. We use J2EE as our technicalinfrastructure to build our components and integrate withWeb service.Keywords: e-learning system architecture; Web Services;J2EE1. INTRODUCTIONE-Learning has grown organically without a clearpicture of the components of a typical e-learning system orhow they interrelate. The need for such architecture iscritical for defining competitive arenas and for standardsdevelopment.Up to this date, proposals are available for thestandardization of information models, such as learningobject metadata, learner profile and content packaging.Those standards provide the needed data structure forimproving interoperability and reusability among e-learning content and system components. There are alsostandards about a conceptual component model of e-learning architecture like LSTC of IEEE [7]. But there is alack of an implementable architecture to define how tocombine the information model with the componentCCECE 2003 – CCGEI 2003, Montreal, May/mai 20030-7803-7781-8/03/$17.00 © 2003 IEEEmodel and how to define an appropriate interface betweeneach component and subsystem to achieveinteroperability.The main objective of this paper is to contribute to thisstandardization process with an original proposal for afunctional architecture to build standard-driven distributedand interoperable learning systems. The functionalarchitecture defines components that make up an e-learning system and the objects that must be movedamong these components. There are some proposals aboutfunctional model, such as SCORM [9], which define ageneral functional model of a learning managementsystem, and Sun Microsystems also present a functionalmodel [6]. Compared with those functional models, ourproposal divides the learning system into a contentmanagement system and a learning management to makethe functional responsibility more clear and try to cover allthe e-learning function components. We also define thelearning objects exchanged between each component,which is related to current existed learning standards.Nowadays there are many e-learning products existingin the market which are implemented using differentplatforms that are not compatible with each others. Forexample, distributed object systems such as MicrosoftsCOM family and the OMG CORBA standard did notinteroperate. Each presented numerous security andadministration challenges when deployed over theinternet, and neither quite met the scalability expectationscreated by the Web. Web Services provide a standardmeans of communication among different softwareapplications, running on a variety of platforms and/orframeworks. The excitement over Web Services is basedlargely on the potential for a combination of XML, theWeb, the SOAP and WSDL specifications, and to-be-defined protocol stacks to address many of the problemsthese technologies have encountered. Web Services aredesigned as a standard reference architecture in order topromote interoperability and extensibility among theseapplications, as well as to allow them to be combined inorder to perform more complex operations [10]. Thispaper focuses on how to integrate Web service on the e-learning application domain.
  • 2. -002-At the end we use J2EE as our technical infrastructureto build our components and integrate with Web Services.There are some researches that focus on e-learningarchitecture. [4] proposes a framework for designing anddeveloping agent-based online learning systems, whichintegrates software agents and learning objectstechnologies. [3] addresses the interoperability problemconsequence of the proliferation of online learningsystems and selects CORBA as the technologicalsupporting infrastructure. [2] presents an open functionalarchitecture based on an analysis of the processesinvolved in managing and delivering educational contentand shows how agent technology can be used to solve theproblem of planning collaborative learning and presentingdidactically optimal content. [1] presents a layeredcomponent model to support Web-based collaborativeapplications. The contribution of this paper is defining aclear functional model of an e-learning system which hasa close relationship with current exist standards and usesthe newly emerging technology of Web Services to solvethe problem of interoperability between different learningsystems.The organization of this paper is as follows. In chapter2, we introduce the current e-learning interoperabilitystandards and specifications. We propose a functionalarchitecture of a standard-driven distributed andinteroperable learning system in chapter 3. In chapter 4,we describe how Web Services are used in a learningenvironment according to the functional model weproposed and how to integrate Web Services into a J2EEplatform.2. STANDARDS IN E-LEARNINGIn general, the purpose of e-learning interoperabilitystandards is to provide standardized data structures andcommunications protocols for e-learning objects andcross-system workflows. When these standards areincorporated into vendor products, users of e-learning canpurchase content and system components from multiplevendors, based on their quality and appropriateness, withconfidence that they will work together effectively [5].Learning standards and specifications can be organizedinto five categories as follows:Metadata: Learning content and catalogs must be labeledin a consistent way to support the indexing, storage,discovery (search), and retrieval of learning objects bymultiple tools across multiple repositories. Data used forthis purpose are referred to as learning object metadata.Several initiatives are creating metadata standards: TheLearning Object Metadata, or LOM of IEEE LearningTechnology Standards [7], and the Dublin Core Metadata.Many other organizations have adopted and adapted LOM.Content Packaging: Content packaging specificationsand standards allow courses to be transported from onelearning system to another. The initiatives dealing withcontent packaging include: The IMS Content Packagingspecification [8], the IMS Simple Sequencingspecification [8], the ADL Sharable Content ObjectReference Model (SCORM) [9].Learner Profile: Learner profile information can includepersonal data, learning plans, learning history,accessibility requirements, certifications and degrees,assessments of knowledge and the status of participationin current learning. The most important effort tostandardize learner profile information is the IMS LearnerInformation Package (LIP) specification [8].Learner Registration: Learner registration informationallows learning delivery and administration components toknow what offerings should be made available to a learner,and provides information about learning participants to thedelivery environment. There are two initiatives currentlydealing with these requirements in e-learning: The IMSEnterprise Specification [8], and the SchoolsInteroperability Framework which supports the exchange ofthis type of data in the K-9 environment.Content Communication: When content is launched, thereis the need to communicate learner data and previousactivity information to the content. Work going on is theADL’s Sharable Content Object Reference Model(SCORM) project based on the CMI specification of theAviation Industry CBT Committee. [9]3. THE FUNCTIONAL MODELTo understand how different systems might worktogether, it is useful to have a simple functional model ofan e-learning application environment. The functionalmodel can provide a visual representation of thecomponents that make up an e-learning environment andthe objects that must be moved among these components.SCORM defines a highly generalized model of a “LearningManagement System” (LMS) as a suite of Services thatmanage the delivery and tracking of learning content to alearner. But it does not specify functionality within theLMS. The functional model we propose is stronglyinfluenced by the SCORM functional model. Wesupplement some functions to make it cover most of thefunctions an e-learning environment should have, for thereason that SCORM only focuses on the function ofdelivery and tracking of learning content in LMS. We alsodivide the LMS which SCORM defined into LCMS(Learning content management system) and LMS(Learning management system) to make each system‘sfunctionality more focused and clear. In the functionalmodel, we also define which standards information shouldbe interchanged among each component. The standardsinformation focuses on the SCORM content model but isnot limited to it. Figure 1 below shows the functional model.
  • 3. -003-Course AuthoringToolsUser ProfileManagerCourseManagerCollaborativeEnvironmentAssess/EvalutionEngineLearnerRegistrationManagerLMSTeacherLearnerProfilerepositoryRemoteServiceRemoteLMSLearner EventsLearner EventsIMS LIPIMS EnterpriseIMS LIPIMS EnterpriseIMS EnterpriseUserUserUserLearning ContentAuthoring ToolsLearning ContentAssemble ToolsLearning ContentManagerDeliveryEnvironment Tracking EngineApIAdapterLCMSContentExpertsContentExpertsContentrepositoryRemoteServiceRemoteLCMSSCORM SCOsASSETsAggregationsSCORM SCOsASSETsSCORMAggregationsSCORM SCOsASSETs CMI APILearnerEventsSCORM SCOsASSETsAggregationsLearnerEventsFig. 1. Functional model of e-learning systemAn LCMS is a multi-user environment where learningdevelopers can create, store, reuse, manage, and deliverdigital learning content from a central object repository.Whereas an LMS manages the processes surroundinglearning, an LCMS manages the process of creating anddelivering learning content, just as the names indicate.LCMS allow users to create and reuse small units ofdigital instructional content. The use of standardizedlearning metadata structures plus standardized learningobject import and export formats also allows learningobjects to be created and shared by multiple tools andlearning repositories. To support this interoperabilityacross systems, LCMS is designed to conform to standardspecifications for content metadata, content packaging,and content communication. Figure 1 shows thecomponents in LCMS and the standard objectsinterchange between those components.LMS needs the interchange of user profile and userregistration information with other systems, the location ofthe course from LCMS and gets the learner action fromLCMS. The components and standard information neededare shown in figure 1.The key to integrate successfully between LMS andLCMS is an open, interoperable approach. In this paper,we introduce an architecture that uses Web Servicestechnology to implement the interoperability between theLMS and LCMS and also between different learningsystems.4. The service architectureFrom the features of Web Services, we know that WebServices are perfectly feasible for implementing theinteroperability of e-learning systems for three mainreasons:• The information exchanged between e-learningsystems like LOM, IMS content packaging, allhave standard XML binding.• Web Services architecture is platform andlanguage independent. It can promoteinteroperability and extensibility among thesevarious applications, platforms and frameworksthat have existed in the real e-learning market.• Web Services provide a unified programmingmodel for the development and usage of privateIntranet as well as public Internet Services. As aresult, the choice of network technology can bemade entirely transparent to the developer andconsumer of the service.Figure 2 shows how Web Services can be used in an e-learning environment.LearningServiceRequesterContentServiceRequester/ProviderLCMSLearningServiceProviderLearnerServiceRequester/ProviderLMSUserServiceRequester/ProviderRemoteLMSContentServiceRequesterRemoteAuthoringtoolsContentServiceRequester/ProviderRemoteLCMSLearnerServiceDiscoveryAgenciesFind/PublishFindFind/PublishFind/PublishFind/PublishPublishInteractInteractInteractInteractContentServiceRequesterContentServiceDiscoveryAgenciesInteractFindFig. 2. Service architecture of e-learning systemThis architecture defines how different e-learningsystems exchange messages through the interaction ofWeb service agents in each system. Service Provider is theplatform that hosts access to the service. It has also beenreferred to as a service execution environment or a servicecontainer. Its role in the client-server message exchangepatterns is that of a server. Service Requestor is theapplication that is looking for and invoking or initiating aninteraction with a service. Discovery Agency is asearchable set of service descriptions where serviceproviders publish their service descriptions. The servicediscovery agency can be centralized or distributed.Standard compliant learning information presented byXML that is wrapped with the SOAP specification isexchanged between the requester and provider. Theprovider publishes a WSDL file that contains a descriptionof the message and endpoint information to allow therequester to generate the SOAP message and send it to thecorrect destination.
  • 4. -004-5. IMPLEMENTATIONNowadays both the J2EE and .Net platform support theimplementation of Web Services. One advantage of usingJ2EE as a base for our system is that we have a muchwider choice of vendors for our pre-built software(application servers mostly), including numerous opensource projects. J2EE is an industry standard. The mostimportant reason for us selecting J2EE is that our othersystems are all java based. No architectural change isneeded when we implement Web Services on J2EE andexisting J2EE components can be easily exposed as WebServices. Many benefits of J2EE are preserved for WebServices such as Portability, Scalability, and Reliability.WebcontainerJSPServletContentAssemble EditContentManagementDelivery ControlLearningRequesterTracking ControlContentManagementControlContent ServiceProviderContent EditContentDeliveryEJB/Data Access BeansSCORM ContentModelBeansSCORM ContentModelBeansSCORM ContentModelBeans SCORM RTEData ModelBeansSCORM RTEData ModelBeansSCORM RTEData ModelBeansContent ServicerequesterLearnerRemoteToolsRemoteLCMSLCMSLMSDatabasesWeb Service Technologies(SOAP,UDDI,WSDL,edXML)Web Service Technologies(SOAP,UDDI,WSDL,edXML)Web Service Technologies(SOAP,UDDI,WSDL,edXML)SQL/JDBC SQL/JDBCHTTPHTTPHTTP HTTPcontentExpertscontentExpertsFig. 3. System architectures of LCMS Using J2EEplatform and Web ServicesBriefly, Figure 3 is a system architecture view of LCMS.It shows how to use Web Services in J2EE architecture.The component in the functional model is decomposedinto several components distributed into different layer.The components with similar function in the same layersare combined into one to provide service to upper layer.The J2EE programming model promotes a model thatanticipates growth, encourages component-oriented codereusability, and leverages the strengths of inter-tiercommunication. It is the tier integration that lies at theheart of the J2EE programming model.6. CONCLUSION AND FUTURE WORKIn this paper, we analyzed the current state of the e-learning standards. Then we proposed a functional modelof an e-learning environment. We also defined thedifferent learning objects exchanged between eachcomponents and cross-system workflows which arecompatible with current existing standards.E-learning standards provide the interoperability betweenlearning systems and tools from different vendors from aninformation viewpoint. But to provide interoperabilitybetween systems on different platforms implemented bydifferent technologies, there must have architecturesupport. Web Services provide a standard means ofcommunication among different software applications,running on a variety of platforms and/or frameworks. Inthe second part of this paper we defined how to use WebServices technology to implement the interoperabilitybetween LCMSs and LMSs. At the end, we gave multi-tiered component-oriented system architecture of LCMSto illustrate how to integrate Web Services into a J2EEplatform. We also defined the business tier of the LCMSsystem, which is compatible with SCORM standards.There are many challenges for implementing such an e-learning system because Web Services and e-learningstandards are all new emerged technology and areundergoing changes and developments. The security ofServices, the encryption of messages, and the commontaxonomies to describe Services and service access pointsin e-learning systems environments are all in need ofconsideration.References[1] L.Anido-Rifon, M.J.Fernandez-Iglesias, M.Llamas-Nistal,M.Caeiro-Rodriguez, J.Santos-Gago “ A Component Modelfor Standardized Web-Based Education” ACM Journal ofEducational Resources in Computing, Vol. 1, No. 2,Summer 2001, Article #1, 21 pages.[2] R. Brussee, A. Salden, P. Boekhoudt, H. van Vliet “A Web-based E-learning infrastructure, ” SSGRR 2001[3] L. E. Anido-Rifón, J. M. Santos-Gago, J. S. Ródríguez-Estévez, M. Caeiro-Rodríguez, M. J. Fernández-Iglesias,Martín Llamas-Nistal, “A Step ahead in E-learningStandardization: Building Learning Systems from Resusableand Interoperable Software Components,” WWW2002[4] F. Lin, P. Holt, L. Korba, and T. K. Shih “A Framework forDeveloping Online Learning Systems,” SSGRR 2001[5] “E-learning Interoperability Standards,” White paper of SunMicrosystems[6] “E-learning Application Infrastructure,” White paper of SunMicrosystems[7] Learning Technologies Standardization Committee (LTSC).Web site at http://ltsc.ieee.org/[8] IMS Global Learning Consortium. Web site athttp://www.imsproject.org/[9] US Department of Defense, Advanced Distributed Learning(ADL) Initiative. Web site at http://www.adlnet.org/[10] The World Wide Web Consortium (W3C) Web site athttp://www.w3.org/