Referencing other resources (especially possibly deleted ones or ones in other locations)

[thomasd-gea]

While talking about the feeding, I came across the point that you could reference a feed that is on location A in a ration that is on location B. I think it will be hard to avoid that by a specification in the schema, but maybe we should give a strict advice to users of the standard? This can of course also happen with an animal event that references an animal on another location (e.g. because it was moved).

A similar thing are references to possibly deleted entities. If you have a ration that references a feed which you don't want to have in your resource list anymore (because you have sooooo many feeds already in there and you don't want to buy this specific feed anytime in the future anymore), then you can not delete the feed as the ration would then become invalid. If the ration becomes invalid, all resources/events that reference it will also become invalid, and the same happens if you just delete the ration as well. On the other hand, if you don't delete things, you will end up with a system containing (possibly) more outdated and unused data than used data. I think we should also think about guidance in this part and (although I know it will get tricky with that) thinking about the deletion of referenced resources in general. Including moved animals.