Enabling full service surrogates using the portable channel representation

The simplicity of the basic client/server model of Web services led quickly to its widespread adoption, but also to scalability and performance problems. The technological response to these problems has been the development of technology for the creation of surrogates for Web servers, starting with simple proxy caches and reverse proxies, and leading more recently to the development of content distribution networks. Surrogate technologies based on caches have proved quite successful in reducing the load due to delivery of cacheable content (HTML files and images), but in general they cannot replicate services that are implemented through the execution of programs at the server. A full service surrogate is a technology that is designed to address this issue directly because it is a copy or mirror of the server that is created, managed and updated automatically. One of the central issues in the creation of full service surrogates is portability of interpreted content, and the representation of metadata necessary to support execution. In this paper we describe the Portable Channel Representation (PCR), which is an extensible markup language/resource definition framework encoded data model developed to enable full service surrogates, and we discuss the implications of the increasing importance of executable Web services.