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Re: Web browsers should preserve the file system Last-Modified time of downloaded files

From: Bjoern Hoehrmann <derhoermi@gmx.net>
Date: Sun, 06 Nov 2011 03:36:13 +0100
To: Brolin Empey <brolin@brolin.be>
Cc: www-tag@w3.org
Message-ID: <h7rbb7lsmdojmdv60s969r8jobuohuj8ch@hive.bjoern.hoehrmann.de>
* Brolin Empey wrote:
>Most GUI Web browsers (maybe most Web browsers, including non-GUI ones?) 
>do not preserve the file system last modified time of downloaded files: 
>  even if the HTTP server sends the Last-Modified response header, the 
>Web browser does not set the last modified time (mtime) field of the 
>downloaded file in the local file system to the Last-Modified time 
>served with the file.  This behaviour effectively *changes* the last 
>modified time of the downloaded file even if the file has not actually 
>been modified.

That's a bit of a narrow view. Some file systems maintain multiple time
stamps for files like the time of creation, the time of the last modifi-
cation, the time of the last read to the file and so on. If you can ma-
nipulate them at will, you might set the "creation" time to the last-
modified value in the HTTP header and a "last access" time to when the
download finished. There is also no way to infer from a last-modified
header what time that designates (other than heuristics perhaps). It may
be for instance that the server, say, creates an archive of various re-
sources on the fly each time you request a resource even though the in-
dividual components of the archive do not change, and neither does the
archive. In the end this seems to be a user interface issue: some might
prefer to have their downloaded files carry the "downloaded" time so
they can find the most recently downloaded files by sorting by date, and
others might want to have the "true" date so they can tell from the file
data how old something really is. Neither seems a wrong choice to me, so
the problem you cite isn't one that can be addressed in a general way.

>I believe implementing this basic file copy functionality should be 
>prioritised above advanced features such as WebGL and Typed Arrays [1]:

Browser vendors listen very carefully to the concerns of their users and
of web authors in general. They largely reject the notion that their own
opinions might not accurately reflect opinions of authors and users. If
they were to accept such a notion, they might have to implement features
in a manner they are unconvinced of. They will fight that with whatever
works, and quite successfully so.
Björn Höhrmann · mailto:bjoern@hoehrmann.de · http://bjoern.hoehrmann.de
Am Badedeich 7 · Telefon: +49(0)160/4415681 · http://www.bjoernsworld.de
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Received on Sunday, 6 November 2011 02:36:41 UTC

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