In order to follow the material in this chapter, you need to know about XML, including namespaces, and you need to know a little about HTTP and Java servlets. You also need to understand XML Schema, because the current type system for WSDL is based on it. In the next section we’ll give an overview and limited introduction to SOAP, WSDL, and JAX-RPC (the Java API for XML-based RPC), but we expect that you’re already somewhat familiar with them.