We study formally the consistency problem, for replicated shared data, in the Action-Constraint framework (ACF). ACF can describe a large range of application semantics and replication protocols, including optimistic and/or partial replication. ACF is used to decompose the consistency problem into simpler sub-problems. Each is easily understood. Existing algorithms from the literature can be explained as combinations of concrete sub-problem implementations. Using ACF, we design a new serialisation algorithm that does not cause aborts and only needs pairwise agreement (not global consensus)