Business process modelling and analysis puts specific requirements on models used and the language for expressing those models. The models should be easily understandable and analysable. In this paper we study the requirements for such a language and introduce a language that satisfies those requirements to a large extent. It was developed in the Testbed project, which aims at developing a systematic approach to business process change. The language, called AMBER, has a graphical representation, and allows to model processes, data, and the organisation and people involved in a uniform and integrated way. On the basis of a formal foundation of the language, different analyses and tool support are available. We illustrate our approach with a realistic example.