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Re: Distributing versions across servers

From: Martin Bernauer <bernauer@big.tuwien.ac.at>
Date: Wed, 4 Jun 2003 15:45:14 +0200
To: <geoffrey.clemm@us.ibm.com>
Cc: <ietf-dav-versioning@w3.org>
Message-ID: <002801c32a9f$869dc8c0$d0a8a8c0@merzouga>

With my e-Mail client HTML emails are hard to answer (quite weird), thus my
answer are marked by ">" (so, the inverse from usual), sorry for that.

-----Original Message-----
From: Geoffrey M Clemm [mailto:geoffrey.clemm@us.ibm.com] 
Sent: Friday, May 30, 2003 4:32 PM
To: Martin Bernauer
Cc: ietf-dav-versioning@w3.org; ietf-dav-versioning-request@w3.org
Subject: Re: Distributing versions across servers

There are two several questions here. 

One is: Can the server store different versions on different servers? 
The answer to this is: yes. 
A server can do whatever it wants in this regard. 
  
> I wouldn't be so sure about that ;)

Another is: Does the protocol provide a way for a client to force the server
to put a version on a particular server? 
The answer to this is: no. 
Different server implementations will have very different policies and
capabilities wrt where and how versions are stored, and any attempt by a
client to "control" this will inevitably result in poor interoperability. 

> That was what I wanted to know. Though I would say this *might*
> result in poor interoperability, depending on facts that are 
> outside the scope of WebDAV. I can think of two interoperability 
> issues:
> (a) the client uses an URI scheme (or URN namespace) the server or 
> other clients can't resolve (b) the client forces the server to store 
> the version on a computer that other clients do not have access to. 
> Sure there are more issues, however, does e.g. a programming language 
> prevent you from writing non-interoperable applications? So it comes 
> down to the question whether it is it the responsibility of WebDAV 
> (and if yes, how far) to enforce interoperability of WebDAV 
> applications. It seems that HTTP wasn't concerned about that so far, 
> it relies on a common adressing scheme (URI) and that's it.

Another is: Can a client hint at what server it would want a new version to
be stored on? 
The answer to this is: yes. 
In particular, a client explicitly creates a version-controlled resource at
a particular location.  A client can create (or at least try to create ...
depends on what the server supports) different version-controlled resources
for a given version history on different servers.  When a user checks in a
given version-controlled resource (or checks in a working resource
checked-out from a given version-controlled resource), a server can take
this as a hint that it would be reasonable to store the new version on the
same server that stores that version-controlled resource. 

> Yes, but  that is not Standard WebDAV...
>
> Thanks for clarification,
> Martin

Cheers, 
Geoff 
Received on Wednesday, 4 June 2003 09:45:19 GMT

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