- From: Yaron Goland <yarong@Exchange.Microsoft.com>
- Date: Sun, 16 Jan 2000 17:43:14 -0800
- To: w3c-dist-auth@w3.org
- Message-ID: <7DE119D3D0E15543874F7561EECBDBED02619E1C@BEG.platinum.corp.microsoft.com>
The last paragraph of section 8 reads: "Although [WebDAV] allows a MOVE on a collection to be a non-atomic operation, the MOVE operation defined here MUST be atomic. Even when the Request-URI identifies a collection, the MOVE operation involves only removing one binding to that collection and adding another. There are no operations on bindings to any of its children, so the case of MOVE on a collection is the same as the case of MOVE on a non-collection resource. Both are atomic." As there is no way to tell the difference between a URI that was mapped through a BIND method and a URI that was mapped through a MKCOL the effect of this paragraph is to re-write RFC 2518 to make MOVE atomic. The issue here is largely a repeat of the issues addressed in Yaron.AtomicDelete. An additional issue, beyond Yaron.AtomicDelete, is that MOVE in most file systems is actually implemented as a copy followed by a delete, at least in the case of directories. Hence file systems can not implement atomic moves. Hence requiring atomic moves means that file systems can not implement WebDAV. Furthermore even though some of the more advanced file systems can handle atomic MOVEs, they can only do so within a single volume. This would mean that a server which had more than one file volume would have to refuse user requests to move files across the volumes solely because it could not do so atomically. Finally, the title of DAV begins with a D for a very specific reason. Requiring atomic behavior on MOVEs will prevent all but the highest end systems from being able to MOVE files between systems because the cooperating systems would have to implement a transactioning system between themselves. As such I move that the atomic MOVE language be struck from the BIND spec on the grounds that it reduces interoperability, requires behavior that would preclude file system based systems from supporting WebDAV and significantly hinders WebDAV's ability to act in a distributed manner.
Received on Sunday, 16 January 2000 20:44:06 UTC