[gme-users] Constraint problem

[Jeff Parsons]

What about the case where GME is used with other tools, for example one
that generates
XML for GME to import. If this tool had a bug and generated something
that violated the
constraint in question, wouldn't "Check All" be the only way to catch
it?


  _____  

	From: gme-users-bounces at list.isis.vanderbilt.edu
[mailto:gme-users-bounces at list.isis.vanderbilt.edu] On Behalf Of Larry
H.
	Sent: Thursday, March 02, 2006 10:32 AM
	To: gme-users
	Subject: [gme-users] Constraint problem
	
	
	I'm having a problem defining a constraint that concerns a
change in number of children in a container.  My intention is to check
this constraint on an event, like "onlostchild", and to prevent the
action by setting the constraint's Priority=1.  My problem is to find an
approach that does not subsequently trigger a violation when the user
chooses the 'Check All' action of the Constraint Manager.
	 
	It is my current belief that there is no way to define such a
constraint.  The reason is that the focus of this constraint is
"change", whereas the focus of the Constraint Manager, in general, is
"current state".   Constraints concerning "change" typically involve
knowing "state before" and "state after".  Have I failed to consider
something?
	 
	One thing that occurs to me is that the Constraint Manager might
consider not checking constraints on "Check All" that are checked on
events with Priority=1.  The intuition is that, since such event-based
constraints can only result in aborting the action, there is simply no
reason to check them again on "Check All".  Such a feature would allow
the desired constraint to be defined quite simply with a "false"
predicate.
	 

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