trouble with trigger/function???

hello.

i have been trying to create a trigger or trigger/function combination but i
have so far been unsuccessful. my task is simple, when someone inserts a
row in the PERSON table, create a row in the RESOURCE table (note that i
have to pass parameters). details below...

first, the basic procedure and trigger are shown here:

CREATE FUNCTION sp_person_resource() RETURNS bool
AS 'insert into resource(rid, name, type, desc) values (1905, ''chris'',
''person'', ''blah''); select true;'
LANGUAGE 'sql';

CREATE TRIGGER trig_person_resource BEFORE INSERT ON person
FOR EACH ROW EXECUTE PROCEDURE sp_person_resource();

i do not know what to use for a return type (i don't really need to return
anything). but when i try to write a trigger to call that fn, it tells me
that the fn must return opaque...i modify my proc but it tells me that "sql
fns cannot return type opaque."

what's going on? and a side question, what is opaque?

thanks
chris