Programming Web Services with XML-RPC

Appendix A. The XML You Need for XML-RPC

The purpose of this appendix is to introduce you to XML. Although with most XML-RPC implementations you won’t ever see the XML representation of the underlying machine-to-machine communications, knowledge of what is going on underneath will help you debug and troubleshoot.

If you’re already acquainted with XML, you don’t need to read this appendix. If not, read on. It’s obviously beyond the scope of this appendix to be a complete reference to XML, but it does present enough information to give you an understanding of how XML is used in XML-RPC.

Note that this appendix makes frequent reference to the formal XML 1.0 specification, which can be used for further investigation of topics that fall outside the scope of XML-RPC. Readers are also directed to the “Annotated XML Specification,” written by Tim Bray and published online at http://XML.com/, which provides illuminating explanation of the XML 1.0 specification; and to “What is XML?” by Norm Walsh, also published on http://XML.com.

What is XML?

XML, the Extensible Markup Language, is an Internet-friendly format for data and documents, invented by the World Wide Web Consortium (W3C). The “Markup” denotes a way of expressing the structure of a document within the document itself. XML has its roots in a markup language called SGML (Standard Generalized Markup Language), which is used in publishing and shares this heritage with HTML. XML was created to do for machine-readable documents on the Web ...