Thanks @surangak for raising this brainstorming discussion. Actually, you are right. We have to be more careful when we select conditions. Those should be meaningful.
Anyway, In create operations (POST) we cannot specify the UUID, right?
So @surangak are you saying this condition is meaningless? I actually don’t know 
. But this is heavily depends on client requirements. And we can’t predict all their requirements. Also I have never seen conditional creates/deletes/updates before 
(have you?) I have only seen conditional GETs:
And the idea of that operation is totally different. We use conditional GETs to check whether a resource has been modified since the last call(or vs some conditions). if it is not modified, we return HTTP 304(not modified), rather than sending the normal response.
So I think we all are new to this “conditional” business. But building up the framework and implementing one or two functions will beneficial for the future.
Are we happy about the conditions that we have already chosen?