This paper proposes a model-based lifecycle for the development of web services, which is based on two kinds of models, collaboration models and service ones. After agreeing upon a collaboration model, which is a public specification, each party can work out a service model and then can turn it into a process written in an orchestration language such as BPEL. As the conceptual gap between a service model and its BPEL implementation is relevant, this paper is concerned with the automatic mapping of service models to BPEL processes, in line with model-based development. Moreover it discusses how to validate services with respect to collaboration models both at-design time and at run-time, and presents the bProgress software environment, which is made up of a number tools developed during this research.