The variation of contexts in which a Web service could be used and the resulting variation in Quality of Service (QoS) expectations makes a clear case for further research to extend Web services management platforms with more sophisticated control mechanisms to cater for differentiated service offerings. However, most Web services platforms are based on a best-effort model, which treats all requests uniformly, without any type of service differentiation or prioritization. This paper presents WS-DiffServ, a service differentiation middleware based on prioritization which leverages service requestor profile to classify service requests. We first explore the typical generic requirements of a differential QoS support in Web services management. We then present in detail the design of a priority based differentiated responsiveness platform for Web services.