Commuting operations greatly simplify consistency in distributed systems.
This paper focuses on designing for commutativity, a topic neglected
previously. We show that the replicas of \emph{any} data type for which
concurrent operations commute converges to a correct value, under some simple
and standard assumptions. We also show that such a data type supports
transactions with very low cost. We identify a number of approaches and
techniques to ensure commutativity. We re-use some existing ideas
(non-destructive updates coupled with invariant identification), but propose a
much more efficient implementation. Furthermore, we propose a new technique,
background consensus. We illustrate these ideas with a shared edit buffer data
type
