Error -742?

IDS 12.10FC12 Solaris 10 1/13 Recently we tried to add a DELETE TRIGGER to a table. Got a -742 error (foreign key with cascade delete cannot coexist with a delete trigger) because the table had a FK with cascading delete. Might anyone explain why a delete trigger cannot coexist with a cascade-delete foreign key? Why wouldn't the cascade delete just cause the delete trigger to fire for each row being deleted by the FK cascade? Maybe there is some kind of logical inconsistency or ambiguity implied by that combination of actions? Thank you. DG