Quality assessment of service providers in a conformance-centric Service Oriented Architecture

In a Service Oriented Architecture (SOA), the goal of consumers is to discover and use services which lead to them experiencing the highest quality, such that their expectations and needs are satisfied. In supporting this discovery, quality assessment tools are required to establish the degree to which these expectations will be met by specific services. Traditional approaches to quality assessment in SOA assume that providers and consumers of services will adopt a performance-centric view of quality, which assumes that consumers will be most satisfied when they receive the highest absolute performance. However, adopting this approach does not consider the subjective nature of quality and will not necessarily lead to consumers receiving services that meet their individual needs. By using existing approaches to quality assessment that assume a consumer's primary goal as being optimisation of performance, consumers in SOA are currently unable to effectively identify and engage with providers who deliver services that will best meet their needs. Developing approaches to assessment that adopt a more conformance-centric view of quality (where it is assumed that consumers are most satisfied when a service meets, but not necessarily exceeds, their individual expectations) is a challenge that must be addressed if consumers are to effectively adopt SOA as a means of accessing services. In addressing the above challenge, this thesis develops a conformance-centric model of an SOA in which conformance is taken to be the primary goal of consumers. This model is holistic, in that it considers consumers, providers and assessment services and their relationship; and novel in that it proposes a set of rational provider behaviours that would be adopted in using a conformance-centric view of quality. Adopting such conformance-centric behaviour leads to observable and predictable patterns in the performance of the services offered by providers, due to the relationship that exists between the level of service delivered by the service and the expectation of the consumer. In order to support consumers in the discovery of high quality services, quality assessment tools must be able to effectively assess past performance information about services, and use this as a prediction of future performance. In supporting consumers within a conformance-centric SOA, this thesis proposes and evaluates a new set of approaches to quality assessment which make use of the patterns in provider behaviour described above. The approaches developed are non-trivial – using a selection of adapted pattern classification and other statistical techniques to infer the behaviour of individual services at run-time and calculating a numerical measure of confidence for each result that can be used by consumers to combine assessment information with other evidence. The quality assessment approaches are evaluated within a software implementation of a conformance-centric SOA, whereby they are shown to lead to consumers experiencing higher quality than with existing performance-centric approaches. By introducing conformance-centric principles into existing real-world SOA, consumers will be able to evaluate and engage with providers that offer services that have been differentiated based on consumer expectation. The benefits of such capability over the current state-of-the-art in SOA are twofold. Firstly, individual consumers will receive higher quality services, and therefore will increase the likelihood of their needs being effectively satisfied. Secondly, the availability of assessment tools which acknowledge the conformance-centric nature of consumers will encourage providers to offer a range of services for consumers with varying expectation, rather than simply offering a single service that aims to delivery maximum performance. This recognition will allow providers to use their resources more efficiently, leading to reduced costs and increased profitability. Such benefits can only be realised by adopting a conformance-centric view of quality across the SOA and by providing assessment services that operate effectively in such environments. This thesis proposes, develops and evaluates models and approaches that enable the achievement of this goal

Agent-based virtual organisations for the Grid

The ability to create reliable, scalable virtual organisations (VOs) on demand in a dynamic, open and competitive environment is one of the challenges that underlie Grid computing. In response, in the CONOISE-G project, we are developing an infrastructure to support robust and resilient virtual organisation formation and operation. Specifically, CONOISE-G provides mechanisms to assure effective operation of agent-based VOs in the face of disruptive and potentially malicious entities in dynamic, open and competitive environments. In this paper, we describe the CONOISE-G system, outline its use in VO formation and perturbation, and review current work on dealing with unreliable information sources

QoS assessment of providers with complex behaviours: An expectation-based approach with confidence

ervice Level Agreements (SLAs) define a set of consumer expectations which must be met by a provider if a contract is not to be broken. Since providers will potentially be providing many different services to thousands of different consumers, they must adopt an efficient policy for resource management which differentiates consumers into service ranges. Existing approaches to QoS assessment of providers assume that the policy of a provider with respect to consumers is handled on an individual basis. We maintain that such approaches are ineffective when providers adopt a policy based on service differentiation and in response introduce and evaluate an expectation-based approach to QoS assessment which presupposes the classification of consumers into ranges defined by their expectation. As well as carrying out assessment to determine the likely future behaviour of a provider for a given consumer expectation, we attach a confidence value to our assessment to indicate the level of certainty that the result is accurate. Our results suggest that our confidence-based approach can help consumers make better informed decisions in order to find the providers that best meet their need

A multiple quality-space mapping approach to QoS assessment

In an open, service oriented environment where multiple providers offering functionally identical services exist, it is desirable that service consumers can make a decision of which service to use based on quality of service (QoS). While considerable effort has been made to develop models and techniques to assist consumers in QoS assessment, the majority of existing approaches tend to ignore consumers¿ expectation on QoS and consider subjective user ratings only in assessment. In this paper, we propose an expectation-based approach which uses delivered values instead of ratings as the basis for QoS assessment. We provide a conceptual overview of our approach, compare it qualitatively with existing methods, and empirically evaluate its performance

Incorporating QoS specifications in service discovery

In this paper, we extend the current approaches to service discovery in a service oriented computing environment, such as Web Services and Grid, by allowing service providers and consumers to express their promises and requirements for quality of service (QoS). More specifically, we allow service providers to advertise their services in an extended DAML-S that supports quality specifications, and we allow service consumers to request services by stating required quality levels. We propose a model here for incorporating QoS specifications and requirements in service discovery, and describe how matchmaking between advertised and requested services based on functional as well as quality requirements is supported in our model

Supporting Formation and Operation of Virtual Organisations in a Grid Environment

The ability to create reliable and scalable virtual organisations (VOs) on demand in a dynamic, open and competitive environment is one of the challenges that underlie the Grid concept and research. In this paper, we describe the agent-based mechanisms that we are currently developing within the CONOISE and CONOISE-G projects for supporting VO formation and operation

Monitoring, Policing and Trust for Grid-Based Virtual Organisations

A key challenge in Grid Computing is the ability to create reliable and scalable virtual organisations (VOs) which operate in an open, dynamic and competitive environment. In response, in the CONOISE-G project, we are developing an infrastructure to support robust and resilient virtual organisation formation and operation. Specifically, CONOISE-G provides mechanisms to assure effective operation of agent-based VOs in the face of disruptive and potentially malicious entities in dynamic, open and competitive environments. In this paper, we describe the architecture of the CONOISE-G system, and provide details of its implementation

Monitoring, Policing and Trust for Grid-Based Virtual Organisations

A key challenge in Grid Computing is the ability to create reliable and scalable virtual organisations (VOs) which operate in an open, dynamic and competitive environment. In response, in the CONOISE-G project, we are developing an infrastructure to support robust and resilient virtual organisation formation and operation. Specifically, CONOISE-G provides mechanisms to assure effective operation of agent-based VOs in the face of disruptive and potentially malicious entities in dynamic, open and competitive environments. In this paper, we describe the architecture of the CONOISE-G system, and provide details of its implementation.

Supporting Formation and Operation of Virtual

The ability to create reliable and scalable virtual organisations (VOs) on demand in a dynamic, open and competitive environment is one of the challenges that underlie the Grid concept and research. In this paper, we describe the agent-based mechanisms that we are currently developing within the CONOISE and CONOISE-G projects for supporting VO formation and operation