RE: Link that deactivate itself, action

Grassel Guido NRC/Hki (guido.grassel@research.nokia.com)
Tue, 04 Nov 1997 09:06:57 +0200

Dear MUG members

Emmanuel BEUQUE wrote yesterday:

::>I have a technical question about links that deactivate itself.
::>
::>Following what it is said at the last sentence of section 53.3, "it is
::>possible for a link to deactivate itself in its LinkEffect. Such an
action
::>shall be postponed until the LinkEffect has been completely executed."
::>
::>This last sentence seems problematic to me. Suppose the linkEffect
::>deactivate itself and then make an action that would cause the link to
fire
::>again it it was active. Shall we understand that we would go into an
::>infinite loop or should we rather considered that :
::>
::>The link is deactivated immediately but all remaining elementary actions
::>keep queued in the execution stack managed by the MHEG-5 engine.
Agree with this sentence.

::>
::>(That's a proposal of modification for section 53.3).
::>
::>To give an example suppose the following objects in a scene :
::>
::>{:IntegerVar 1
::> :OrigValue 1
::>}
::>{:Link 2
::> :EventSource 0
::> :EventType IsRunning
::> :LinkEffect (
::> :Activate (3)
::> :TestVariable (1 2 0)
::> )
::>}
::>{:Link 3
::> :InitiallyActive false
::> :EventSource 1
::> :EventType TestEvent
::> :EventData true
::> :LinkEffect (
::> :Deactivate (3)
::> :Activate (4)
::> :TestVariable (1 1 1)
::> )
::>}
::>{:Link 4
::> :InitiallyActive false
::> :EventSource 1
::> :EventType TestEvent
::> :EventData true
::> :LinkEffect (
::> :Deactivate (4)
::> :Run (5)
::> )
::>}
::>{Bitmap 5
::> :InitiallyActive false
::> ...
::>}
::>
::>
::>What would be the behaviour of this scene when it is running ?
::>
::>-link 3 testVariable action generates a new event that matches link 3 and
4.
I would expect this to happen! The TestVariable event generated upon
execution of the LinklEffect of Link 3 matches the LinkCondition of Links 3
and 4, but only Link 4 fires because to my understanding Link 3 has been
deactivated before the TestVariable action gets axecuted.

Regards & see you in Sydney
Guido

-----------------------------------------------------------------
Guido Grassel guido.grassel@research.nokia.com
Nokia Research Center tel/fax: +358 9 4376-6827/6855

mailing address: location:
P.O. Box 422 Itälahdenkatu 22b
FIN-00045 Nokia Group 00210 Helsinki-Lauttasaari
Finland