XML : Alternative method of invoking an XSL stylesheet

Probably the most simple way of invoking an XSL stylesheet is by adding a second line to any XML-file, something like this:

  <?xml-stylesheet type="text/xsl" href="yourstylesheet.xsl"?>    

However, I've heard about other methods - preferably a method that does not require any tampering with the XML-file and not tied up to any particular platform (open format solution).

Any suggestions?

Many thanks in advance.

/Paul