Introduction to XML

Clearly XML is an essential ingredient of Service-Oriented Architecture. Service definitions are expressed via XML documents, the data structure of messages is defined through XML documents, configuration for the run-time infrastructure is, by and large, in XML, the contents of messages sent between services and service consumers is XML based, and the SOAP envelope that wraps the message itself is also—you guessed it—an XML document. In order to delve into doing SOA, there are a few things you should know about XML. For now, let’s assume you have dealt with XML in the past. For a basic introduction into XML, as well as a list of other resources with in-depth information on XML, see Appendix B.

Much of the attraction of XML lies in the fact that in all major application-development technologies, tools, and platforms, facilities are available for performing the most frequently needed operations on XML. Whether you develop in JavaScript, PHP, Java, C#, or PL/SQL for the JEE, .NET, or Oracle Database platform, you will have native language facilities help you process XML documents. These operations performed on XML documents are: