Get started with XPath

This tutorial introduces XPath and covers most aspects of it. It is aimed at people who do not know XPath or want a refresher. If you plan to use XSLT, you should take this tutorial first. You will learn: What XPath is, the syntax and semantics of the XPath language, how to use XPath location paths, how to use XPath expressions, how to use XPath functions, and how XPath relates to XSLT. XPath is a W3C standard. This tutorial covers version 1.0.

http://www-106.ibm.com/developerworks/edu/x-dw-xxpath-i.html?S_TACT=104AHW06&S_CMP=EDU