e-Learning is becoming an influential role as an economic method and a flexible mode of study in the institutions of higher education today which has a presence in an increasing number of college and university courses. e-Learning as system of systems is a dynamic and scalable environment. Within this environment, e-learning is still searching for a permanent, comfortable and serviceable position that is to be controlled, managed, flexible, accessible and continually up-to-date with the wider university structure. As most academic and business institutions and training centres around the world have adopted the e-learning concept and technology in order to create, deliver and manage their learning materials through the web, it has become the focus of investigation. However, management, monitoring and collaboration between these institutions and centres are limited. Existing technologies such as grid, web services and agents are promising better results. In this research a new architecture has been developed and adopted to make the e-learning environment more dynamic and scalable by dividing it into regional data grids which are managed and monitored by agents. Multi-agent technology has been applied to integrate each regional data grid with others in order to produce an architecture which is more scalable, reliable, and efficient. The result we refer to as Regionally Distributed Architecture for Dynamic e-Learning Environment (RDADeLE). Our RDADeLE architecture is an agent-based grid environment which is composed of components such as learners, staff, nodes, regional grids, grid services and Learning Objects (LOs). These components are built and organised as a multi-agent system (MAS) using the Java Agent Development (JADE) platform. The main role of the agents in our architecture is to control and monitor grid components in order to build an adaptable, extensible, and flexible grid-based e-learning system. Two techniques have been developed and adopted in the architecture to build LOs' information and grid services. The first technique is the XML-based Registries Technique (XRT). In this technique LOs' information is built using XML registries to be discovered by the learners. The registries are written in Dublin Core Metadata Initiative (DCMI) format. The second technique is the Registered-based Services Technique (RST). In this technique the services are grid services which are built using agents. The services are registered with the Directory Facilitator (DF) of a JADE platform in order to be discovered by all other components. All components of the RDADeLE system, including grid service, are built as a multi-agent system (MAS). Each regional grid in the first technique has only its own registry, whereas in the second technique the grid services of all regional grids have to be registered with the DF. We have evaluated the RDADeLE system guided by both techniques by building a simulation of the prototype. The prototype has a main interface which consists of the name of the system (RDADeLE) and a specification table which includes Number of Regional Grids, Number of Nodes, Maximum Number of Learners connected to each node, and Number of Grid Services to be filled by the administrator of the RDADeLE system in order to create the prototype. Using the RST technique shows that the RDADeLE system can be built with more regional grids with less memory consumption. Moreover, using the RST technique shows that more grid services can be registered in the RDADeLE system with a lower average search time and the search performance is increased compared with the XRT technique. Finally, using one or both techniques, the XRT or the RST, in the prototype does not affect the reliability of the RDADeLE system.

This thesis presents an approach to design, specify, validate, verify, implement, and evaluate composed web/grid services. Web and grid services can be composed to create new services with complex behaviours. The BPEL (Business Process Execution Language) standard was created to enable the orchestration of web services, but there have also been investigation of its use for grid services. BPEL specifies the implementation of service composition but has no formal semantics; implementations are in practice checked by testing. Formal methods are used in general to define an abstract model of system behaviour that allows simulation and reasoning about properties. The approach can detect and reduce potentially costly errors at design time. CRESS (Communication Representation Employing Systematic Specification) is a domainindependent, graphical, abstract notation, and integrated toolset for developing composite web service. The original version of CRESS had automated support for formal specification in LOTOS (Language Of Temporal Ordering Specification), executing formal validation with MUSTARD (Multiple-Use Scenario Testing and Refusal Description), and implementing in BPEL4WS as the early version of BPEL standard. This thesis work has extended CRESS and its integrated tools to design, specify, validate, verify, implement, and evaluate composed web/grid services. The work has extended the CRESS notation to support a wider range of service compositions, and has applied it to grid services as a new domain. The thesis presents two new tools, CLOVE (CRESS Language-Oriented Verification Environment) and MINT (MUSTARD Interpreter), to respectively support formal verification and implementation testing. New work has also extended CRESS to automate implementation of composed services using the more recent BPEL standard WS-BPEL 2.0.

Made available in DSpace on 2016-06-02T19:05:35Z (GMT). No. of bitstreams: 1 2565.pdf: 3480971 bytes, checksum: d77b25ab6ff234cafc2664267466f051 (MD5) Previous issue date: 2009-05-25 / Financiadora de Estudos e Projetos / Existing mechanisms for Grid Service (GS) security control do not allow transparently binding different user roles and permissions in the access control for operations and resources. After successfuly authenticated a user may access all registered services. This dissertation presents the GS Security Architecture (GSSA), a security architecture for GSs based on the Open GSs Architecture (OGSA), which aims to fullfil this gap. GSSA also provides funcionalites for authentication, log keeping for non-repudiation, auditing and accountability, secure data exchange between GS, and the execution of GSs from withn Web Services (WS). This dissertation also describes an implementation of the GSSA, named GS Security Proxy (GSSP), and evaluates the use of this proxy in a telemedicine application. / Mecanismos disponíveis para segurança de Grid Service (GS) não permitem associar, transparentemente, diferentes papéis de usuários a diferentes permissões no controle de acesso às operações e recursos. De maneira geral, uma vez autenticado em um sistema, um usuário tem acesso a todos os serviços definidos. Esta dissertação apresenta GS Security Architecture (GSSA), uma arquitetura de segurança baseada na Open GSs Architecture (OGSA), que visa a suprir esta deficiência. GSSA também fornece funcionalidades para autenticação, registro de log para não repúdio, auditoria e responsabilização (accountability), integridade e confidencialidade das mensagens trocadas entre os GSs e a execução de GSs a partir de Web Services (WS). Esta dissertação descreve também uma implementação de GSSA chamada GS Security Proxy (GSSP) e avalia o uso deste proxy em uma aplicação da telemedicina.