I'm not sure I understand correctly what you mean by assuming everything to be a "MyLink" but that's not always possible. It depends first on how deep the rabbi

I'm not sure I understand correctly what you mean by assuming everything to be a "MyLink" but that's not always possible. It depends first on how deep the rabbit hole you want to go with dereferencing URLs - what logic will you employ to decide what level of dereference to full objects you stop at, and, more importantly on being authorized to access the objects pointed at by said URL. Sometimes ActivityPub activities come with properties that are IRIs that when dereferenced are giving you 404 or 401. What does your middleware do then: Retry, Abort, Fail? Also, I'm not sure I agree with your thesis that business logic needs to worry only about a single type of object, because the ActivityPub specification recognizes all of the types I mentioned in my first reply as being "valid" and if you consider their superset as being the "canonical type" you'll be wasting quite a lot of storage (memory and disk wise) when all you have access to is the plain URL.