Subject: Ftp-WG: Last Call on MLST is over ...

From: "Paul V Ford-Hutchinson" <[email-masked]>
Date: Wed, 19 Dec 2001 11:19:02 -0500

Brad Clements wrote:

> You may also wish to add a cautionary statement that using MDTM to 
> determine the existance of an object or the validity of a path is 
> not appropriate.

I'm struggling to make my thoughts clear here - but ....

how about "FTP command responses and object existance are not related" The 
only thing a command-response does is tell you about that command and the 
response _at that time_ by the time the next command is being processed - 
things may have changed.

For example, I have an FTP server that doesn't reflect a filesystem at 
all, it reflects a 'receive and delete' mailbox.  I.E. the act of a 
succesful RETR is that the object has gone.  I don't consider that this 
breaks the FTP protocol at all.  What it does sometimes break is client 
assumptions about the server. 

I think FTP is pretty good at trying to stop the client assuming things 
because UNIX/Windows/MVS/... does it that way. 

If a client uses MDTM (or DELE, or SITE CHMOD, or anything) to assume a 
generally applicable change or discovery of state of an object - that is 
OK - but an FTP server that doesn't share the same view of the world is 
not in violation of FTP, nor should we try to spec FTP to make it so.

Paul

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Paul Ford-Hutchinson :  eCommerce application security : 
[email-masked]
MPT-6, IBM , PO Box 31, Birmingham Rd, Warwick, CV34 5JL +44 (0)1926 
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