As we saw in our web services examples in and , one of the most interesting directions for XML is web services. A web service is simply an app service supplied over the network, making use of XML to describe the request and response. Normally, web services run over HTTP and use an XML-based protocol called SOAP (Simple Object Access Protocol), an evolving W3C standard. The combination of XML and HTTP provides a universally accessible interface for services. SOAP and other XML-based remote procedure call mechanisms can be used in place of Java RMI for cross-platform communications and as an alternative to CORBA. There is a lot of excitement surrounding web services, and it is likely that they will grow in importance in coming years. To learn more about Java APIs related to web services, check out the networking chapters of this tutorial and take a look at . That's it for our brief introduction to XML. There is a lot more to learn about this exciting new area, and many of the APIs are evolving rapidly. We hope we've given you a good start.