Simple Object Access Protocol (SOAP) version 1.1 is an industry standard designed to improve cross-platform interoperability using the Web and XML. The Web has evolved from simply pushing out static pages to creating customized content that performs services for users.

A user can be a customer retrieving specialized Web pages for placing orders or a business partner using a customized form for reviewing stock and sales figures. A wide range of components located on various computers are involved in performing these Web-based services. Because these systems consist of many computers, including the client computer, middle-tier servers, and usually a database server, these systems are called distributed systems. To understand how SOAP works, let's take a look at the distributed system first.