[relax-ng] Competitive analysis

Team - as I work up materials for the half-day tutorial in December
on RELAX I'm gleaning and contrasting and comparing.

Here's an article on W3C Schema from IBM's web site - clearly
good items here to show RELAX strengths against.

  http://www-106.ibm.com/developerworks/xml/library/x-sbsch.html

What does nill="true"  mean anyway?!? ; -)

DW.