The REST architectural style has attracted a lot of interest from industry due to the nonfunctional properties it contributes to Web-based solutions. SOAP/WSDL-based services, on the other hand, provide tools and methodologies that allow the design and development of software supporting complex service arrangements, enabling complex business processes which make use of well-known control-flow patterns. It is not clear if and how such patterns should be modeled, considering RESTful Web services that comply with the statelessness, uniform interface and hypermedia constraints. In this article, we analyze a set of fundamental control-flow patterns in the context of stateless compositions of RESTful services. We propose a means of enabling their implementation using the HTTP protocol and discuss the impact of our design choices according to key REST architectural principles. We hope to shed new light on the design of basic building blocks for RESTful business processes.

Service descriptions allow designers to document, understand, and use services, creating new useful and complex services with aggregated business value. Unlike RPC-based services, REST characteristics require a different approach to service description. We present the Resource Linking Language (ReLL) that introduces the concepts of media types, resource types, and link types as first class citizens for a service description. A proof of concept, a crawler called RESTler that crawls RESTful services based on ReLL descriptions, is also presented.