[gme-users] Constraint problem

[Larry Howard]

Both of these are legitimate reasons to use the feature I propose with
diligence, but not for disallowing it.  Indeed, from the point of view of my
intended use they are both irrelevant.  The amended feature proposal does
not require any changes to how folks are using GME's constraint manager
today.  It just opens up some additional possibilities.  What's wrong with
that?

-----Original Message-----
From: gme-users-bounces at list.isis.vanderbilt.edu
[mailto:gme-users-bounces at list.isis.vanderbilt.edu] On Behalf Of Matthew J.
Emerson
Sent: Thursday, March 02, 2006 12:22 PM
To: gme-users
Subject: RE: [gme-users] Constraint problem



Similarly, what about the case where you build a large model, then go back
and edit the paradigm to include a constraint like the one you describe
after-the-fact. The constraint could never be evaluated for the existing
cases where it might be violated.

 

--Matt

 


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From: gme-users-bounces at list.isis.vanderbilt.edu
[mailto:gme-users-bounces at list.isis.vanderbilt.edu] On Behalf Of Jeff
Parsons
Sent: Thursday, March 02, 2006 12:20 PM
To: gme-users
Subject: RE: [gme-users] Constraint problem

 

If incorrect XML is generated and imported into GME, and the part of the
model corresponding to 

the incorrect XML is not modified by the modeler, what event would trigger
the check?

 


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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 12:15 PM
To: gme-users
Subject: RE: [gme-users] Constraint problem

Thanks Jeff, this helps clarify my proposal.

 

I propose instead the ability to say that a constraint should be checked
exclusively on the associated events.  

 

I think that this would put things nicely into the hands of the
meta-modeler.

-----Original Message-----
From: gme-users-bounces at list.isis.vanderbilt.edu
[mailto:gme-users-bounces at list.isis.vanderbilt.edu] On Behalf Of Jeff
Parsons
Sent: Thursday, March 02, 2006 10:56 AM
To: gme-users
Subject: RE: [gme-users] Constraint problem

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?

 


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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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