Service Quality Model Evaluation

Service Quality Model Evaluation

Fotis Aisopos (National Technical University of Athens, Greece), Magdalini Kardara (National Technical University of Athens, Greece), Vrettos Moulos (National Technical University of Athens, Greece), Athanasios Papaoikonomou (National Technical University of Athens, Greece), Konstantinos Tserpes (National Technical University of Athens, Greece) and Theodora Varvarigou (National Technical University of Athens, Greece)
Copyright: © 2012 |Pages: 15
DOI: 10.4018/978-1-60960-827-9.ch004
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Abstract

In this chapter, we present the current state-of-the-art technology and methodologies regarding the evaluation of the provided quality of service in service oriented environments. With the emergence of service provisioning infrastructures and the adoption of Service Level Agreements acting as electronic contracts between service providers and customers, the need to control and validate the offered quality has appeared throughout the service lifecycle. This monitoring is performed either in the client side, using the customer’s Quality of Experience and employing trust and reputation mechanisms for the service selection and evaluation phase, or in the provider side, dynamically reconfiguring the service and allocating resources accordingly, in order to optimize the quality metrics guaranteed. The latter, of course, initially requires mapping of the high-level quality parameters, which are closer to the customer perception, to low-level computing terms related to the resource management process. Dynamic resource allocation based on quality monitoring and evaluation can lead to optimizing resource utilization and provider’s profits.
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Service Quality Modeling

In the beginning of 2000 a term has been coined perhaps more than any other in relation to Quality of Service (QoS) and Service-Oriented Computing (SOC), that is, of the Service Level Agreement (SLA) (Tian, Gramm, Naumowicz, Ritter, & Schiller, 2003), (Sahai, Machiraju, Sayal, Jin, & Casati, 2002), (Keller & Ludwig, 2002). Of course, the term itself had been defined a long time ago as “… an agreement between the provider of a service and its customers which quantifies the minimum quality of service which meets the business need” (Hiles, 1994). In short, SLAs are the formalization of a provable, quantitative assessment of QoS upon which both the provider and the consumer negotiate and agree. Upon agreement the provider must commit the necessary resources so as to satisfy the consumer requirements. The consumer is then able to evaluate the outcome of the service against the set of SLA terms. There are various negotiation models that differentiate this procedure. The main differentiation axes (Figure 1) are the lifetime of the SLAs and the granularity of the SLA terms. The differentiation mainly affects the side (provider or customer) that has to do the evaluation and in turn the side which is more susceptible to SLA violations (normally these sides are opposites).

Figure 1.

Variety in SLA models. The further right we move on the “SLA lifetime” axis, the more a provider has to reserve its resources for the customer. The further up we move on the “granularity” axis, the closer we get to the use of terms that match the customer's understanding

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