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W3C note available on how to avoid the lost update problem using HTTP/1.1

From: Henrik Frystyk Nielsen <frystyk@w3.org>
Date: Tue, 11 May 1999 17:54:53 -0400
Message-Id: <>
To: w3c-dist-auth@w3.org

Hi there,

I have published a note on how to avoid the lost update problem using
HTTP/1.1 and why it is also needed by Webdav. Please read and comment!


It is linked from


ps: Although not required, it helps if you use a browser that understands
<OBJECT> tag when reading this.


   Avoiding the lost update problem has been a notorious challenge when
   editing documents remotely on the Web using HTTP/1.0. While WebDAV
   provides an extended set of services for editing the Web, HTTP/1.1
   provides a minimal set of hooks for avoiding the lost problem by
   detecting when versions have changed so that changes aren't lost in
   the editing process. While simple, these hooks are fundamental to
   editing the Web using HTTP/1.1 and are needed in Webdav as well.
   This Note explains a) how to use HTTP/1.1 to detect the lost update
   problem using preconditions and strong etags and b) how to avoid
   problems with HTTP/1.0 clients that do not know about these features
   but only use plain HTTP PUT requests. Neither a) nor b) requires any
   changes to HTTP/1.1, but can be achieved using existing features.
   The mechanism has been implemented in [21]Web Commander and [22]Amaya
   (both using [23]libwww), and [24]Jigsaw - all [25]W3C Open Source
   software freely available to all interested parties.
   Detection is only one of several ways to avoid the lost update problem
   and this document discusses the pros and cons of various other
   mechanisms including exclusive locks and immutable revisions.

Have fun,

Henrik Frystyk Nielsen,
World Wide Web Consortium
Received on Tuesday, 11 May 1999 17:55:01 UTC

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