Suppose I want to build a RESTful interface to an ACID system. I want to allow the user to incrementally change the state of the system, but only "commit" the changes when he is satisfied with their sum. I imagine a user GETting a resource, POSTing some changes to it which may have side effects on other resources, GETting other resources to observe the side effects, and eventually committing to the changes or rejecting them. It's easy enough to take care of ACD because these happen on the server and are transparent to REST, but I'm not sure how would one ensure Isolation. Two users who are GETting the same resource should see different things depending on which transaction each of them is in. I can't see a way to do this except to add something like ?transaction-id=0x234BD2037 to every URI which would expose completely unnecessary implementation details to the user.

Am I thinking of this in the wrong terms?

Ari.