Updating views

If I add a "where" clause on my views, I can't insert or update them
anymore. Why?

Example:
CREATE TABLE temp (a int);
CREATE VIEW tview AS SELECT a FROM temp WHERE a>10;

INSERT INTO tview VALUES (13);
ERROR:  Cannot update a view without an appropriate rule

What is the appropriate rule?

--
Rasmus Resen Amossen | stud.mat.dat at the University of Copenhagen
Jagtvej 120, -244    | http://www.math.ku.dk/muh
2200 Kbh. N          | http://w1.1444.telia.com/~u144400001