• Suppose some other person wants to read our XML document.
• Suppose that their XML reading program requires only part of the data ...
• ... or it requires the XML to be written in a different way.
• It would be useful to describe how one XML document can be transformed into another one.
• This is one of the roles of the eXtensible Style Language (XSL).
• This is called an XSL Transformation (XSLT).
• As HTML is close to XML, XSL is often used to transform XML into HTML.