SOAP (Simple Object Access Protocol)
Simple Object Access Protocol (SOAP) is an industry standard designed to improve cross-platform interoperability using the Web and XML.

The XML Document Object Model
The XML Document Object Model (DOM) is a platform-neutral and language-neutral interface that allows developers to create applications and scripts to access and update the content, style, and structure of XML documents.

Access Your iTunes Music Library via XML
One problem being addressed with XML is not very hard at all, and is actually quite fun. I'm referring to Apple's iTunes digital music service, which you probably didn't realize had anything to do with XML. In this tutorial, you'll learn how to: How XML fits into Apple's iTunes digital music service.