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K. Ari Krupnikov wrote:
> 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.
If the scope of the potential side effects is small and well-defined, you
might be able to reduce everything to a single exchange: get all of the
potentially-affected state to the client in a single XML document (or
collection of XML documents), allow the client to make changes locally until
satisfied, then post the modified state back to the server. Since
modifications live on the client side until committed, there is no need to
come up with any separate URL scheme.
This approach would work for, say, a movie database, where the user might
check out a full movie description to change the director's name, then check
the entire description in again. It might not work so well for, say, a
geographical database, where a modification to a shoreline may also require
corrections to landuse data, roads and railroads, and so on, in no
It is entirely possibly that your project is one in the second category, but
I wouldn't give up on the simpler approach until it were proven inadequate.
Stupid-and-easy usually wins: moving 50K of XML each way once can be much
more efficient than many 100 byte transactions.
All the best,