Towards a comprehensive view of web services QoS models

In a growing web services environment, the usage, design and composition methods of web services require proper and reliable information about web services quality. Quality-of- Service (QoS) is usually referred to the non-functional characteristics of web services which can be used as an important role to differentiate between different web services. In order to select the best web services among those with similar functionality, it is important for the web requester to have a mechanism to rank them and also from the service providers side to ensure that their web services are according to the agreed QoS. Currently there is no standard manner to define the QoS characteristics of web services. Many studies have shown different categorization of QoS which led to the issue of semantic interoperability of QoS. One way to understand the QoS, is to identify all its possible requirements for web services. This paper is an attempt to explore some of the QoS issues which are essential for web services. It first proposes a QoS framework which suggests considering QoS for web services along four different views. Each view is representing a particular relevant facet of QoS models. The main contribution of this paper is to show that there is a big quantity and variety of interpretations of various service quality concepts and models and gives the reasons why there is no holistic QoS modeling approach.