UML Qos profile exploration for the specifications of a generic QoS metamodel for designing and developing good quality web services

• Main Author: Rahman, Wan Nurhayati
• Published: University of Salford 2010
• Subjects: 004
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521552

The work developed and reported in this thesis aims at contributing to research related to the Quality of Service (QoS) for the web services field. More specifically, this work investigates the possibility of using the Unified Modeling Language (UML) as a specification language for QoS requirements. We started this research by reviewing the state-of-the-art on the use of UML as a metalanguage for QoS description and specification. This research provided a comprehensive review and description of the QoS specifications that comprise some already existing factors contributing to the QoS and some newly proposed ones. These include availability, accessibility, reliability, integrity, service time, security, performance, transaction, execution price, capacity, regulatory and reputation. Furthermore, the research has proposed a QoS metamodel as a lightweight extension to the Web Service Description Language (WSDL) to incorporate the selected QoS specifications into web services' functionalities. The main question this research is trying to answer is, "What makes a web service better than other web services providing the same functionality?" Hence, the aim of this research is two fold, first it helps designers and developers to provide better web services and second, it helps web services users to select the best web service for their applications. The QoS metamodel illustrates what functionalities and how they can be extended with the proposed QoS specifications. The basic WSDL specification consists of definition element as the root, and other elements that include types, message, portType, binding, service and import. All of these elements describe the functionality of a web service. This research sees the possibility of extending the WSDL specification to include a set of QoS specification to describe the non- functional requirement of a web service. These QoS specifications are vital as an augmentation to the existing WSDL specification to assure high quality web services development and implementation. The QoS metamodel could be used to realize the incorporation of the selected QoS specifications into the WSDL. Both the QoS specifications and the QoS metamodel can be used as reference model for service providers, designers, developers and users on how to provide, use and select good quality web services. The QoS metamodel is meant to be general and flexible. Therefore, it is not to restrict specific service providers or the use of a certain technique, language or implementation approach. We have illustrated a possible use of the QoS specifications and implementation of the model by using a case study. However, we do not provide a full implementation of the web services in the case study, as we do not intent to manage a real Electronic Commerce (EC) application that deal with the actual business activity. Time constraints, inadequate sources and technical problems were the factors behind this limitation. Alternatively, we have conducted controlled experiments that involved novice and experienced users as the validation method to give a practical experience to users in designing high quality web services. The results from the validation and evaluation processes have shown that the research contributions are important and practical in nature. The outcome from the research gives many advantages including encouraging the inclusion of quality requirements in the design to help service providers to design and develop better quality web services through the WSDL extension at the initial stage. We conclude by stating that we have achieved the research objectives, come out with an original contributions and added knowledge to the web services QoS field.