@J.D. This is a big concern. My initial thought was that having so many possible combinations will make it costly and error prone to check certain conditions. Is cat in a car? I need to check cat-car, cat-carrier-car, cat-carrier-box-car and cat-box-car. Listing all cats in a car has also that many combinations. Ultimately, I think I'll need to do it with separate tables and helper views. I had an idea and wanted to check if it is any good.

Hi. Unfortunately cat and car are not the only important things. I will have a lot of situations where cat is put into carrier and only later possibly put into a car. Also, boxes are often filled with cats and carriers while being moved one way and empty while going back. And I need to carefully monitor both of those situations.

@Akina Thanks for the edit, I do not know why th tables were bad. I have also specified the conditions of illogical situations.