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A distributed Service Oriented E-Learning Environment based on Grid Technology Hajar Kashfi [email protected] CEIT Department Islamic Azad University of Qazvin Qazvin,Iran

Mohammda Reza Razzazi [email protected] CEIT Department Amirkabir University of technology Tehran,Iran

Key Words: Grid, Resource Sharing, E-learning, Web service, service oriented architecture. Abstract In recent years, there has been a growing interest to reduce costs of establishing learning environment systems. Few administrators have the resources necessary to address e-learning complex issues in a way that enable wide-spread standardize use of the technology across the institutions. E-learning systems consist of complex activities. Most of them are being designed based on client/server, peer to peer; and recently Web Services architectures. These systems have major drawbacks because of their limitations in scalability, availability, distribution of computing power and storage system, as well as sharing information between users that contribute in these systems. This paper will outline the efforts that have be done to address these issues by proposing the use of grid technology as scalable, flexible, coordinated and secure resource sharing among geographically distributed individuals and institutions, in the context of e-learning. Meanwhile, by implementing our middleware based on web service technology, we are able to reuse functionalities. This way, many service providers and content providers can contribute in developing a very large scale integrated e-learning system.

Introduction The emergence of the internet had great impact on e-learning due to the fact that it is an effective and economical medium for making information available to dispread individuals. Especially, it has radically changed the way in which people learn, teach and train (Resmer,1998). Today, learning content can be made available even in remote places and without the need to travel to the site where content is delivered (Pankratius,2003). E-Learning systems have been topics of increasing interest in recent years. The number of users who are interested in e-learning increases daily. These users have many different interests and objectives, and they will need to access to a huge amount of information. Learners vary significantly in their prerequisites, their abilities, their goals for approaching a learning system, their pace of learning, their way of learning and time and money they are able to spend on learning. Therefore, a successful system will be one that addresses all issues for all type of users across the world. Such a system should be scalable, available, interoperable, extensible, and adaptable, and indeed, it should be based on novel technologies. Since such systems are very huge, many organizations and institutes should contribute to the construction of these systems (Sun,2002). This way, development costs of these systems will highly decrease. Few administrators have the resources necessary to address elearning complex issues in a way that enable wide-spread standardize use of the technology across the institutions. One of the main objectives of e-learning systems is to make information accessible to any type of users (Resmer,1998). E-learning systems consist of complex activities. Current efforts for the next generation e-learning architectures are aiming for a transition from e-learning as an integrated, centrally controlled system to a dynamic configurable federation of educational services and information collections (Pankratius,2003) . Treating all systems in the e-learning platform as services that deliver some utility to other services is the fundamental principal behind the service level abstraction (Sun,2002). Therefore, developers adapt their systems to novel

technology trends and developments including technologies like Web services (Booth,2003) and the Grid (Foster,1998a) as well as new paradigms like Peer-to-Peer networking and Service oriented architectures. So, currently, most of e-learning systems are being designed based on client/server, peer to peer; and recently Web Services architectures. These systems have major drawbacks because of their limitations in scalability, availability, distribution of computing power and storage system, as well as sharing services and information between users and organizations contributing in these systems (Pankratius,2003) . This paper reports the efforts that have been done to develop an E-learning grid middleware. By proposing the use of grid technology as scalable, flexible, coordinated and secure resource sharing among geographically distributed individuals and institutions (Foster,2001) in the context of e-learning, we are able to address these concerns. Our middleware focused on Grid as well as using agent (Luck,2002) and web service (Newcomer,2002) technologies to provide developers an integrated infrastructure facilitating E-learning system development. Meanwhile, by implementing our middleware based on web service technology, we are able to reuse functionalities. This way, many e-learning service providers and content providers can contribute in developing a very large scale integrated e-learning system. The reminder of this paper is structured as in the following: section 2 gives some background information in Grid technology, section 3 describes web services. In section 3, there is some information in the field of software agents. In section 5 next generation e-learning systems is exposed. Section 7 discusses our proposed middleware architecture, and finally, section 8 contains the conclusion. Next Generation E-Learning Systems In the area of e-learning (Vossen,2003), recent efforts concentrate on the reuse of application functionalities. However most of these efforts in e-learning such as (IMS,2005) have been focused on the reuse of learning material, a few of these researches have tried to introduce web service as a preferable technology in this area (Pankratius,2003) . Some E-learning systems use advantages of new features offered by Web services such as integration of heterogeneous applications, publicity of available services, etc. As the adoption of this new technology increases, it will become necessary to offer intermediary platforms that make it easier to find and locate services and composing new services from the existing ones (Rodriguez,2003). The success of e-learning has promoted the proliferation of different kinds of e-learningrelated software applications (Rodriguez,2003). Next generation e-learning systems will use Web services that can match learning content to user context in a way that provides a customized, personalized experience. Information retrieval (IR) functions that serve a critical role in many eleaning systems can be distributed or their functions be made available through the web services framework (FU,2004). Also, by using web services, developers can provide the flexibility a learner needs in tertiary education in which many institutions offer courses for education (Vossen,2003). Till now, E-learning and grid technology were two distinct areas. However, E-learning increasingly addresses learning resources sharing, interoperability and various modes of interactions ,and it is the convergence point of grid technology and distance learning (Reklaitis,2001). In contrast with current e-learning applications which may use high performance computing as a secondary task, modern e-learning systems can use novel

technologies such as grid and parallel computing as well as web services to reach interactive, collaborative and reality based learning environments (Reklaitis,2001). By proposing the use of grid technology, many service providers and content providers can participate in various VOs. Using the concept of virtual organization in Grid, we can effectively group users and organizations especially for cooperative learning. Organizations and institutes that contribute in developing such a system can share their resources and services forming different VOs. These organizations can cooperate under some policies to reach their common objectives. Here, we need a middleware for uniform access to all theses resources that belong to different administrative areas. Additionally, an infrastructure is needed that insure availability, scalability, security, extensibility and interoperability for implementing such distributed systems. Each organization should be able to reuse functionalities and services as well other resources that are provided by other organizations. Grid Technology Grid is coordinate resource sharing and problem solving in dynamic multi-institutional virtual organizations (Foster,1998b). An important issue that should be mentioned is that: “the sharing that we are concerned with is not primarily file exchange but rather direct access to computers, software data, and other resources” (Foster,2001). As it has been mentioned in (Foster,1998a), this sharing is necessarily highly controlled and under some sharing rules. A set of individuals and/or institutions defined by such sharing rules form Virtual Organizations (VOs). An actual organization can participate in one or more VOs by sharing some or all of its resources. This resource sharing is conditional: each resource owner makes resources available, subject to constraints on when, where and what can be done (Foster,2001). The background concept in grid is not new. As a real of fact, the collaboration and sharing of resources in a geographically distributed environment is an idea existed since the computer domain originated. In grid, people will be able to easily access to unlimited resources connected through the Internet. Mechanisms for creating, managing, and exchanging information among entities called grid services. The next generation of scientific experiments and studies, popularly called as e-Science (Jennings,2001), will be carried out by communities of researchers from different organizations that span national and international boundaries. Grid computing (Foster,1998b) enables aggregation and sharing of resources through by bringing together communities with common objectives and creating virtual organizations (Foster,2001). Data Grids have evolved to tackle the twin challenges of large datasets and multiple data repositories at distributed locations in data-intensive computing environments (Chervenak,2000). Current e-learning systems are very limit; for example, it is vastly impossible to compute, photo-realistic visualizations in real-time and display the computation result on a remote screen (Pankratius,2003) with the advanced functionality of an e-learning grid, students could be provided with the possibility to search, visualize and accomplish other high computational elearning services in an effective way. Web Services Internet is now almost service oriented and based on messaging and standards for XML interfaces to enable coordinate use of distributed resources. This leads to high level of interoperability in such heterogonous distributed environment. As a result, the basic concept and

building block for internet computing becomes the Web service. A service in this context is a network-enabled entity that provides some capabilities.(Reklaitis,2001) Service-based architectures take legacy application functionality and expose it to the internet in a reliable, highly available, scalable, flexible, manageable, and secure manner, easy and reliable internet-based method to create and access learning. Web Service technology has emerged as a new paradigm of distributed computing. They are layered on the top of standard transfer protocols for transmitting messages that currently, the most common ones are the XML-based specification SOAP (Simple Object Access Protocol), UDDI (Universal Description, Discovery and Integration), and WSDL (Web Service Description Language) (Booth,2003). This concept is illustrated in figure-1. A web service is a stand alone software component that has a unique URI (Uniform Resource Identifier). Figure 1. Web service

Web services present another alternative distributed computing infrastructure which is strongly promoted as a preferable one in contrast with the use of distributed object middlewares such as Java RMI or CORBA (Booth,2003). Web services to Grid services A Grid can be defined as a layer of networked services that allow users single sign-on access to a distributed collection of computing, data and application resources. Grid services allow the entire collection to be seen as a seamless information processing system that the user can access from any location (Chervenak,2000). A Grid Service is a Web Service which conforms to a set of conventions (interfaces and behaviors) that define how a client interacts with a Grid Service. Therefore, Grid Services are standard Web Services with improved characteristics. Two advantages of web services framework that are mentioned in (Foster,1998b) as important reasons for using web services in Grid are: First, the need to support the dynamic discovery and composition of services in heterogeneous environments. Second, the widespread adoption of web services mechanisms means that a framework based on web services can exploit numerous tools and extant services. Virtual educational organizations in E-learning Grid A general agreement exists regarding roles played by people in a learning environment and also the core functionality of modern e-learning platforms. These roles are as follows: Learner, trainer, administrator, and the author. Authors (who may be teachers or instructional designers) create content, which is stored under the control of a learning management system (LMS) and typically in a database. Existing content can be updated, and it can also be exchanged with other systems (Pankratius,2003) .

As we have mentioned in third section, the concept of VO has introduced in grid technology. An actual organization can participate in one or more VOs by sharing some or all of its resources (Foster,2001). Since there are mainly three groups of users in an e-learning environment: learners, tutors, and teachers, there should be various VOs in our grid to cover all types of these users’ needs. There should be some organizations that join students with same learning interests. Another VO is one that connects teachers working on same research areas. The third VO should provide authors cooperation in providing learning contents, and so on. As we have mentioned before,in these VOs, resource sharing is conditional; that is, each resources owner makes resources available subject to constraints on when where and what can be done. For instance one university may let professors of two other universities use its learning services, or even, one author may allow some other authors to reuse one’s learning objects just in special period of time, and maybe on some financial restrictions. Reuse Learning services and learning content through Grid Content consumed by learners and created by authors is commonly handled, stored, and exchanged in the form of learning objects (LOs). Basically, LOs are units of study, exercise, or practice that can be consumed in a single session, and they represent reusable granules that can be authored independently of the delivery medium and can be accessed dynamically. Learning objects can be stored in a database and are typically broken down into a collection of attributes. In a similar way, other information relevant to a learning system (e.g, learner personal data, learner profiles, general user data, etc.) can be mapped to common database structures (Pankratius,2003) . Reusable learning objects (RLOs) are building blocks of a personalized learning experience. RLOs are individual objects, each with their own identity, type, size, and complexity, that can be entered into a database or knowledge repository utilizing metadata description. Recently, many efforts have been done to convert RLOs to Grid Learning objects. A Grid learning object extends the functionality of a traditional learning object by adding grid functionality consisting of a specific grid application layer (Pankratius,2003) . Therefore, we see that there is daily increasing convergence between grid and e-learning technologies. An effort to accomplish this issue is in progress by our research group. Proposed E-Learning Grid Middleware Our middleware is a grid middleware that has some specialized services for e-learning systems. As it has been shown in figure.1, there are four main layers in this middleware. Like middleware that has been exposed in (Foster,2001), the most bottom layer (grid core services layer) itself is consist of four major grid middleware layers including: fabric, connectivity, resource and collective layers. We have implemented our middleware using agent technology, while we tried to represent each agent as a web service (Avila-Rosas,2003) to benefit from these two major technologies both at the same time. Therefore, our middleware is a multi agent system which represents grid core services for resource sharing and other basic services for e-learning (Suzuki ,2002a), (Suzuki ,2002b). Each agent in this middleware is created, deployed and published as a web service. This way, any institution or individual will be able not only to share her content with other grid users, but also to be able to publish her various services across the entire e-learning grid.

The first step in developing such architecture is to provide a grid infrastructure. Users incrementally, add their hosts to the grid. On the other hand, system administrators can add new mediator servers to the system anytime needed to extend the system in desired scale. In this architecture, the entire grid is divided into multiple administrative areas. In each area, a group of agents are responsible to serve some clients that are under control of that area. For each area, there is one mediator server, that response to all requests of clients in that area. There are multiple agents hosting on each mediator server. The most important agent is a mediator agent that is responsible for coordination of other agents. This agent connects fabric agents, which are under its control, to the entire grid. Also, this agent is responsible for creating other manager agents that should exist on each mediator server to provide e-learning and Grid core services. Figure 2. E-Learning Grid middleware Layers

E-Learning basic services layer is the heart of this E-Learning grid middleware. In this layer, agents represent basic services for e-learning using other agents that exist in grid core services layer. Using these agents, users are able to access and share all types of information including papers, magazines, e-books, etc. with other users. As a real of fact, except sharing other resources (hardware resources such as CPU Power and storage media), any user can contribute in publishing learning content in this system. On the other hand, any organization can publish its learning content to its members as well as other organizations. In this layer, basic functionalities of e-learning system are provided. There are multiple agents that cooperate with each other to perform desired services. In figure.2 layers of this architecture has been shown. By using our middleware, different organization and institutes will be able to cooperate with each other to create a large scale distributed learning environment. Using core services that are provided in this middleware, any type of users can join to the grid, and use its services. Organizations aiming to create a complete library and educational environment can use this middleware to structure their resources and to cooperate with other organizations that exist in the Grid. They will be able to create their own additional services and publish them to others as web services. Conclusion Our middleware builds on the assumption that typical e-learning systems are collections of activities or processes that interact with users and suitably chosen content. This enables us to subdivide the main functionality of these systems into a number of stand-alone applications, which can then be realized individually or in groups as Web services. Web services, on the other hand, are offered by a number of providers. These providers can cooperate under some policies in the form of some VOs to reach their common objectives. In this architecture, individuals (containing all e-learning roles) and organizations can cooperate to establish a distributed learning environment. We proposed a middleware for uniform access to all theses resources that

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