[Esml-users] Event ports with null event refs

Feng Shi fengshi at isis.vanderbilt.edu
Mon May 10 14:19:47 CDT 2004


In ESML model, the ComponentType models contained in ComponentTypes
folder are defined as the archetype model, while the ComponentType
models in Interaction diagram are the instances of these archetype

If the EventTypeRef refers to null object, it means that the event port
attached with it can subscribe or publish any type of event. If the
EventTypeRef refers to a specific type of event, then the event port can
only subscribe or publish the same type of event.

ESML allows user to set the EventTypeRef refer to specific event type
for instance model, like TACTICAL_STEERING. Meanwhile, such reference
can also be set in archetype level, like BM__ModalComponentImpl, and it
will propagate to its all instance model.

Hope this helps,


-----Original Message-----
From: Jesse Greenwald [mailto:jesse at cis.ksu.edu] 
Sent: Monday, May 10, 2004 1:08 PM
To: esml-users
Subject: [Esml-users] Event ports with null event refs


I've been taking a look at some of the example models that are included
with ESML.  While looking at them, I've noticed that some event ports on
some components have null event type refs.  That is, when I double click
on EventTypeRef box attached to the port, the following error message is
displayed: "Unable to show referred object of null reference".  Is this
an error in the model, or does this have a special meaning?

One example of this can be found in the MC__ModalSP model.  The ANY_pub
port of the BM__ModalComponentImpl has a null event type reference. 
But, when I double click TACTICAL_STEERING (from Interaction ModalSP_3)
and open up the component, it has a non-null event type ref.


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