How can I use UNION in VIEW/RULE?

I have 2 table say c1,c2 (same attributes) and then I would like to

CREATE VIEW c AS
SELECT * FROM c1
UNION
SELECT * FROM c2;

But the system not accept. (not implement)
Then I change to use
CRATE TABLE c (<** attributes are same as c1,c2 **>)
CREATE RULE r1 AS ON SELECT to c
DO INSTEAD
SELECT * FROM c2
UNION
SELECT * FROM c1;

Tbe system accept this rule but when I process 'SELECT * FROM c1;', the
result is not sastified; only tuples on c2 are display.

Is there other way to get result like above. One I've thought in mind is:-
CREATE RULE r1 AS ON SELECT to c
DO INSTEAD
SELECT funct_UNION(c1,c2);
But I have no idea how to do kinds of the function that return set of
tuple

WChart.