Web service development and usage has shifted from simple information processing services to high-value business services that are crucial to productivity and success. In order to deal with an increasing risk of unavailability or failure of mission-critical Web services we argue the need for advanced reservation of services in the form of derivatives.The contribution of this paper is twofold: First we provide an abstract model of a market design that enables the trade of derivatives for mission-critical Web services. Our model satisfies requirements that result from service characteristics such as intangibility and the impossibility to inventor services in order to meet fluctuating demand. It comprehends principles from models of incomplete markets such as the absence of a tradeable underlying and consistent arbitrage-free derivative pricing.Furthermore we provide an architecture for a Web service market that implements our model and describes the strategy space and interaction of market participants in the trading process of service derivatives. We compare the underlying pricing processes to existing derivative models in energy exchanges, discuss eventual shortcomings, and apply Wavelets to analyze actual data and extract long- and short-term trends.