Sr:
 
  I have tried to look at the postgreSQL www and contact some people but 
i don't 
have full internet just e-mail so it's a little hard to search exactly what
i'm looking for, please help me to find out about this if you can:

	1) There are primary keys, foreing keys and not null statements 
for postgres?
        2) There is possible to emulate this things with the rule system?
	3)How can i get a manual about the system rules for postgres?
			Regards
				Otto