The World Wide Web has evolved from being a pure information repository to a more functional and service oriented platform using technologies such as Web Services. Web service
has been widely employed in e-business, e-government, automotive systems, multimedia services, process control, finance, and a lot of other domains. Quality-of-Service (QoS) is usually employed for describing the non-functional characteristics of Web services and employed as an important
differentiating point of different Web services. With the prevalence of Web services on the Internet, a thorough awareness of the Web service QoS is becoming more and more important. In this article, an overall description of Web Services QoS requirements is presented.