How to Solve a Distributed System Problem in a General Way

The problem cannot be solved in a general way that gives you a distributed system that behaves like a sequential system. CRDTs attempt to model all of the operations that have happened and then they have a merge function on how concurrent conflicting operations would be handled. The more popular design choice for sets in practice is kind of an add wins set because it mimics the behavior of a set where you can't actually issue removal operations until you've seen an element in the set.