From: 'ar...@cogsci.ed.ac.uk@INTERNET@wtgw'(K. Ari Krupnikov)
User A GETs a resource and edits it. User B GETs a resource and edits
it. User A PUTs the modified resource back. User B PUTs her version of
the modified resource back, unaware of A's edits. A's edits are lost
without anyone noticing. What I want to happen is B to get a 409
"Conflict" or some such.
This seems identical to the WebDAV use cases.
A simple way to achieve this is just to use strong entity tags and HTTP
If-Match headers when sending the PUT. This will avoid overlapping
updates if all clients co-operate.
If this is not the case, WebDAV locks can be used as additional security
measure (note that this will not help if A PUTs back after B is done).