Many Web services need customer's private information involving in. In order to take into account the privacy concerns of the individuals, organizations (e.g Web services) provide privacy policies as promises describing how they will handle personal data of the individual. However, privacy policies do not convince potential customers %individuals to disclose their personal data, do not guarantee the protection of personal information, and do not provide how to handle a possible evolution of the policies. In this paper, we introduce a framework based on an agreement as a solution to these problems. It contains a privacy model defined in the policy level of the agreement. The framework supports in the negotiation level of the agreement a lifecycle management which is an important deal of a dynamic environment that characterizes Web services. A negotiation protocol is proposed that enable ongoing privacy negotiation to be translated into a new privacy agreement.