The discussions of Simon and Sara on validation control
remind me of the problem of associating stylesheets with 
XML documents.  (See http://www.w3.org/TR/PR-xml-stylesheet).
The current approach works for simple systems today; it
will be a mistake later.  

Forced embedding of control information in the data (er..document)
goes against a fundamental strength underlying XML.  The
style sheet concept underlying XML seeks to separate content 
from display.  There are two ways to win with separated style 
sheets:

  1) A powerful and wonderful Style controls many lowly XML docs.

         *Style*
       /  |   |  \
     x1  x2  x3  x4

  2) A critical and valuable XML doc flows through many styles to glory.

          *XML*
        /  |  |  \
       s1  s2 s3 s4

Clearly embedding control info works for the first case; that is 
today's web publication model.  The second case just cannot use 
embedded control; this is the data conversion world.



John.
______________________________________________________
John J. Barton          email:  John_Barton@xxxxxxxxxx
MS 3U-6  Hewlett-Packard Labs                                    
1501 Page Mill Road              phone: (650)-236-2888 
Palo Alto CA  94304-1126         FAX:   (650)-813-3381


 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list