The Acumen software design blog provides you with helpful articles about XML.

Several web sites provide a good overview.

Official XML Introduction

XML Wikipedia

XML: Element-Centric or Attribute-Centric?

XML  XML Element or Attribute-Centric? There are numerous articles on the web discussing the advantages and disadvantages of attribute-centric versus element-centric XML. Most correctly come to the conclusion that “it depends” and provide…