Traditionally, workflow management systems aim at alleviating people's burden of coordinating repetitive business procedures, i.e., they coordinate people. Web service orchestration approaches, instead, coordinate pieces of software (the web services), hiding the human aspects that are intrinsically present in any business process behind the services. The recent emergence of technologies like BPEL4People and WS-HumanTask, which introduce human actors into service compositions, manifest that taking into account the people involved in business processes is however important. Yet, none of these approaches allow one to also develop the user interfaces (UIs) the users need to concretely participate in a business process. With this paper, we want to go one step beyond state-of-the-art workflow management and service composition and propose an original model, language and running system for the composition of distributed UIs, an approach that allows us to easily bring together UIs, web s...