As more and more web services that provide the same functionality are developed, it is a major issue to consider not only the functional requirements but also the non functional requirement (NFR) during web service discovery process. The NFR define the Quality of Service (QoS) of the system. Much work has been done on web service discovery process that considers the functional requirements as selection criteria. However not many service discovery strategies consider the QoS properties. On the basis of our study and survey, we advocate that the best performance is achieved by use of both functional and NFR properties. We believe that the user NFR should be expressed explicitly to aid in selecting a web service that best fulfils them. To support this claim we present a detailed survey of web service discovery systems that makes use of QoS factors. Paper also highlights the importance of ontology to represent the non functional requirements in web service discovery. We emphasize how Ontology if built and refined by domain experts can be used for web service discovery process with the purpose of reuse and improved design. © 2012 IEEE.