Year

2012

Degree Name

Doctor of Philosophy

Department

School of Information Systems and Technology

Abstract

This thesis aims to support the management of Service Level Agreement (SLA) of Service-based system (SBS). Service-oriented Architecture (SOA) is the referred architecture to design and develop a SBS. Ideally, SLA provides the means to specify the obligations related to Quality of Service (QoS) by the concerned service roles (i.e., service consumer, service provider) in composing and enacting SBS.

This research addresses three main aspects related to the temporal issues, identified as the SLA life-cycle management, the SLA verification and generation functionality and the SLA violation-impact analysis functionality.

In the aspect of SLA life-cycle management, this research introduces an integrated model of the core process components, the data components and the external parties to fulfil the management of SLA life-cycle. This model can support the development of SLA management system for SBS. In addition, this research explicitly classifies the temporal constraints involved in this model based on the relevant contexts. Some of the contexts are the service roles (i.e., service consumer and service provider), SLA life-cycle stages (i.e., establishment and enactment) and SLA violation stages (i.e., before and after violation). This classification is of significance towards providing a formal model of temporal constraints. In relation to the SLA management aspect, this research proposes and discusses a theoretical framework. This framework focuses on the temporal-aware SLA management for SBS. The framework becomes the foundation to connect the other works in the thesis. The case-study evaluation shows the feasibility of the proposed framework for managing SLA lifecycle of SBS.

In the aspect of SLA verification and generation functionality, this research proposes two inter-related approaches to enable the SLA negotiation activity. The SLA verification aims to support the decision activity of service consumer negotiator (SCN). The verification aims to detect temporal inconsistency and unsatisfactory of temporal constraints defined in a composite SLA offers. The inconsistency issue may potentially occur due to SOA characteristic namely the loose coupling of the involved service providers which have no direct communication. In addition, the unsatisfactory issue can potentially occur when the proposed composite SLA offers are not able to fulfil the temporal requirements imposed by the service consumer. Meanwhile, the SLA generation aims to support the decision activity of service provider negotiator (SPN). The generation aims to generate the appropriate temporal constraints included in the SLA offers. The service provider imposes these temporal constraints to emphasize its resource capacity within time segments. Two aspects involved in determining the appropriate temporal constraints. The first aspect is to attain the temporal requirements in the SLA requests. This is essential to increase the acceptance of SLA offers. The second aspect is to arrange the resource availability effectively. Although this is still at the negotiation stage, considering the resource aspect can potentially reduce the risk of SLA violation that might occur during the actual service execution. The experimental evaluation advocates the effectiveness of the proposed approach.

In the aspect of SLA violation-impact analysis functionality, this research proposes an approach to supporting the SLA violation handling during SLA enactment. The violation can be caused by various reasons such as delay. As a result, the violation needs to be effectively handled by understanding the impact caused by the violation. This information is crucial since it can affect the recovery process in terms of the number of services to be changed and the execution time. The impact information can be used to prioritise the critical area in the composition process for recovery. There are two potential negative impacts from the temporal dimension namely the inconsistency and unsatisfactory condition. By the impacts reasoning, the critical area can be obtained which contain the violated service and the directly impacted services. If the recovery can be performed in the smallest critical area, subsequent change to future services or the entire composition can be avoided. This thesis contributes the SLA violation-impact analysis approach. The experimental evaluation proves the effectiveness of the proposed approach.

Based on the thesis outcomes, the thesis can contribute significantly to the SLA management research agenda in service-based systems. In addition, this research has the potential to foster the wider adoption of SOA in the real world by addressing the practical issues related to the temporal aspect of service offering.

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