Controllership can be determined implicitly from national law, even for an official journal that only publishes data as it receives, including when that journal doesn't have a legal personality (but note my comment on this!).
The definition of 'controller' is broad and you're liable for all processing, done directly or by others on your behalf, including processors. Joint controllership is determined by facts, not contracts. Know your role(s)!
The definition of 'controller' is broad and includes legal persons, who are liable for any violations committed by any person in their business who act on their behalf. DPAs must demonstrate that you acted with intent or neglect to fine you and must base the max amount on the group's total revenue.