Software engineers realize the power of employing common design patterns when building software components. What is much less known, however, is that a similar technique may be applied to software system architecture as well, including web services architecture, and with similar results. Software architecture researchers call such patterns architectural styles. This paper compares and contrasts two architectural styles for web services - Remote Procedure Call (RPC) and Representational State Transfer (REST) - across several dimensions including scalability, flexibility and ease of implementation. The paper also explores the applicability of each style to common usage scenarios via alternative implementations of real-world web services such as Electronic Business using eXtensible Markup Language (ebXML) and Universal Description, Discovery and Integration (UDDI).