Commit rules or Commit trigger

I am developing a temporal database and I have the necessity to control the
integrity constraints befor the commit of the transiction.
I cannot use the deferrable checking because the integrity constraints is a
select and i cannot use the trigger or rule because
the event parameter not support the commit event.
You have some idea?

Thanks

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Claudio Tognolo
claudio(dot)tognolo(at)gmail(dot)com
Department of Computer Science - Verona, Italy
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