If the server is expecting concurrent updates, there is no reason why the server cannot require the use of etags/conditionals; in which case, the server could simply reject the PUT with a bad request or conflict response.
As a general fyi... I've been considering drafting up an informational RFC that describes how a subset of WebDav could be used with APP to enable things like Locking.
- James Eric Scheid wrote:
Say someone develops a really simple APP-client, one which doesn't bother keeping track of ETags and doesn't bother sending PUT updates with an If-Match header ... what can an APP-server do to protect itself from such a client PUTting an out of date version and stomping on a more recent version PUT by some other user? e.
