data modeling question

I asked a question similar to this a couple of weeks ago, but the
requirement has changed a bit and I want to be sure I'm designing my
tables correctly.

I have the following table:

CREATE TABLE workorder (
number VARCHAR(8),
quantity INTEGER,
generic BOOLEAN,

PRIMARY KEY (number)
);

If generic is true, number will need to be associated with at least
one other number in the same table. I need to ensure the integrity of
this association. So, I'm thinking a second table:

CREATE TABLE generic (
gnumber VARCHAR(8),
number VARCHAR(8),

PRIMARY KEY (gnumber, number),

FOREIGN KEY (gnumber)
REFERENCES workorder(number)
ON DELETE RESTRICT
ON UPDATE CASCADE,

FOREIGN KEY (number)
REFERENCES workorder(number)
ON DELETE RESTRICT
ON UPDATE CASCADE
);

Any better way of doing this?

--
Brandon