Table constraints

Hi everybody,
I saw a couple of messages regarding rule/constraint/trigger standards
which Tom proposed to adopt in postgres. I've read through the current
specs, but still can't figure it out. I am using version 7.1.3 and this
is what I am trying to do:
I have 2 tables:
Set { type_id int,       set_desc varchar(128) }
Type { id int primary key }

I want to update a row in Type table and cascade this update to update
Set table. I declare a constraint as follows:
ALTER TABLE Set
ADD CONSTRAINT fk_type
FOREIGN KEY (type_id)
REFERENCES Type (id)
ON UPDATE CASCADE;
Postgres gives me a NOTICE and creates the constraint.

Here are some questions:
Why pg_relcheck table is still empty after the constraint is added?
Why instead it created 5 triggers (I checked pg_class.reltriggers for
Set table): 3 called "fk_type" on Set and 2 unnamed on Type?
Why when I try to update id in Type table I get RI violation error?
Shouldn't it cascade the update?
How can I drop the constraint now? I set reltriggers to 0 in pg_class
entry corresponding to Set table, and tried to delete generated
triggers, but since only 3 out of 5 have "fk_type" name, I couldn't
figure out how to track down the rest of them.

Thanks in advance for any help.

Oleg