DOCBOOK-APPS: XML and PSGML

Hello,

I don't know (X)Emacs, and I would like to try it to write XML files and
debug some XSL stylesheets.

The problem I have is that the rendering done by PSGML (colored
keywords) works only for files with the .sgml extension. Files with .xml
extension are not recognized. I know that it is not really a docbook
related problem, but if someone can give some advice...

I use:
* XEmacs 21.1.9
* PSGML 1.2.2

Thanks.

BG