RE: switch toggles conditional on XPath expressions?

This also applies to group.
-----Original Message-----
From: Jeremy Johnson [mailto:jeremy.johnson@imtc.gatech.edu] 
Sent: Wednesday, June 11, 2003 12:24 PM
To: www-forms@w3.org
Subject: RE: switch toggles conditional on XPath expressions?


I've learned that an XForms user interface will commonly render a form
control bound to a data item only if the 'relevant' property of the data
item is true, thus producing the effect on form controls that I desire.
 
thanks,
 
.:j:.
 
-----Original Message-----
From: Jeremy Johnson 
Sent: Wednesday, June 11, 2003 2:50 PM
To: www-forms@w3.org
Subject: switch toggles conditional on XPath expressions?
 
I'm a complete XForms novice, so please forgive me if I am missing something
considered "obvious".
 
I would like to toggle a switch based on the evaluation of an XPath boolean
expression, but I don't see a construct of XForms mechanisms that can
accomplishing such.
 
The effect I'm trying to achieve is this:  I want form controls to only be
visible when an arbitrary XPath boolean expression evaluates to true,
analogous to the "readonly" property that may be applied to model items,
however I want to ensure that an associated form control does not appear on
screen at all, not simply rendered disabled.  These controls would appear /
disappear as items in the data model take on new values.
 
My original thought was to surround each control with a <switch> element and
have an action respond to all value changes which would conditionally (based
on an XPath expression) toggle each control to "appear" or "disappear".
Unfortunately, I'm unsure of a way to achieve the conditional toggle.
 
Is there another way to accomplish such an effect?
 
Any suggestions would be most welcome.
 
Thanks,
 
  .: jeremy.johnson@imtc.gatech.edu :.
.: interactive.media.technology.center :.
  .: georgia.institute.of.technology :.