PRIMARY KEY (`foreign_db`,`foreign_table`,`foreign_field`)
This makes much more sense. (The same foreign key can be in many tables, but it must always refer to the same primary key.)
hmm i don't think so, in your example clearly the order is the master table and the articles are in a detail/slave whatever you might call it table. of course the column in the mastertable that links to the details table is called foreign key, but because it links _to_ a foreign table, so articles is this foreign table that it links to.