Emerging as the popular choice for leading Internet companies to expose internal data and resources, RESTful Web services are attracting increasing attention in the industry. While automating WSDL/SOAP based Web service composition has been extensively studied in the research community, automated RESTful Web service composition in the context of service-oriented architecture (SOA), to the best of our knowledge, is less explored. As an early paper addressing this problem, this paper discusses the challenges of composing RESTful Web services and proposes a formal model for describing individual Web services and automating the composition. It demonstrates our approach by applying it to a real-world RESTful Web service composition problem. This paper represents our initial efforts towards the problem of automated RESTful Web service composition. We are hoping that it will draw interests from the research community on Web services, and engage more researchers in this challenge.