Re: Temporal Databases

On Wed, Mar 08, 2006 at 12:56:38 -0300,
  Rodrigo Sakai <rodrigo.sakai@poli.usp.br> wrote:
> Ok, but actually I'm not concerned about logging old values. I'm concerned
> about checking temporal constraints. Entity Integrity (PK) and Referential
> Integrity (FK).

Did you see the reference to 'Developing Time-Oriented Database Applications
in SQL' (http://www.cs.arizona.edu/people/rts/tdbbook.pdf) in a recent thread?
That should give you some trigger code you can use to do this kind of thing.
It isn't postgres specific, but shouldn't need too much work.