|Abstract|| ||The REST architectural style is emerging as an alternative technology platform for the realization of service-oriented architectures. In this paper, we apply the notion of composition to RESTful services and derive a set of language features that are required by composition languages for RESTful services: dynamic late binding, dynamic typing, content-type negotiation, state inspection, and compliance with the uniform interface principle. To show how such
requirements can be satisfied by an existing composition language, we include a case-study using the JOpera visual composition language. In it, we present how to build a composite application (DoodleMap) out of some well-known, public and currently existing RESTful service APIs.