OUTER JOIN

Hallo,

I need to port some SQL from Oracle to PostgreSQL v7.2, but I am finding
problems with outer joins.

Here are the tables:
select * from shift_type
id | order_num | from_time | to_time | disabled
----+-----------+-----------+----------+----------
1 | 1 | 06:00:00 | 14:00:00 | f
2 | 2 | 14:00:00 | 22:00:00 | f
3 | 3 | 22:00:00 | 06:00:00 | t
6 | 6 | 00:00:00 | 23:00:00 | f

select * from shift_desc
app_language_id | shift_type_id | description
-----------------+---------------+-------------
1 | 1 | Morning
1 | 2 | Afternoon
1 | 3 | Night
2 | 6 | SHIFT_DE
1 | 6 | SHIFT_EN

and here is the SQL for Oracle:
SELECT ST.id, ST.order_num, ST.from_time, ST.to_time, ST.disabled,
SD.description
FROM shift_type ST, shift_desc SD
WHERE ST.id = SD.shift_type_id(+) AND SD.app_language_id(+) = 2
ORDER BY ST.order_num

The expected result should be:
id | order_num | from_time | to_time | disabled | description
----+-----------+-----------+----------+----------+-------------
1 | 1 | 06:00:00 | 14:00:00 | f |
2 | 2 | 14:00:00 | 22:00:00 | f |
3 | 3 | 22:00:00 | 06:00:00 | t |
6 | 6 | 00:00:00 | 23:00:00 | f | SHIFT_DE
with description populated with NULL, as app_language_id not found.

It seems that Oracle's outer joins work on the basis the single record,
while PostgreSQL don't.
How to do it?

Thank you for your attention,
Marco Roda