Web Services versus Distributed Objects: A Case Study of Performance and Interface Design

Web services are promoted as a new model for distributed systems, yet many skeptics see them as simply a poor implementation of traditional remote procedure calls (RPC) or distributed objects. Previous comparisons support the skeptics: Web services are shown to be significantly slower than RPC, and they lack features like automatic proxies. However, these studies are biased because they are based on an RPC communication style. Web services support a document-oriented style of communication that performs well even in the face of the high latency found in Internet or business transactions. We investigate these issues by comparing the design and implementation of a small file server application implemented using RMI and Web services. For this application, using the most straightforward implementation in both technologies, Web services outperform RMI when accessing multiple/deeply nested files, especially over high-latency channels. However, the default Web services interfaces are awkward to use, so we develop a technique for wrapping the Web service to make it as easy to use as the distributed object implementation. The same wrappers are then used to implement the document-oriented communication style in RMI, which improves performance but significantly complicates the design. This case study provides a more detailed comparison of the relationship between Web services and distributed objects