DataasaService(DaaS)buildsonservice-orientedtechnolo- gies to enable fast access to data resources on the Web. However, this paradigm raises several new privacy concerns that traditional privacy models do not handle since they only focus on the service interface with- out taking into account privacy constraints related to the data exchanged with a DaaS during its invocation. In addition, DaaSs compositions may reveal also privacy-sensitive information. In this paper we propose a pri- vacy formal model in order to extend DaaS descriptions with privacy capabilities. The privacy model allows a service to define a privacy policy and a set of privacy requirements. We propose also a privacy-preserving DaaS composition approach allowing to verify the compatibility between privacy requirements and policies in DaaS composition. We validate the applicability of our proposal with some experiments.