[thelist] xml and rss question

I am redesigning a very small content management system
for my small site and want to experiment a little
with xml.

In simple terms, instead of copy-pasting html in
a form, I want my friends to put articles in xml
tags. 

I want something a DTD(?) like RSS, but designed for articles and that is a
standard or at least used somewhere else so that i can exchange articles
with other people/sites.

Anyone know of a DTD like this ?

On other note, i want to store this xml in a DB
and combine it with xsl to create the actual
pages, that will be stored in another table of the
DB. 

I am using php. I know this is possible, I just dont
know how. 

Any help is appreciated.