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Re: Negative last modified

From: Henrik Frystyk Nielsen <frystyk@w3.org>
Date: Mon, 25 Jan 1999 17:02:20 -0500
To: www-lib@w3.org
Message-ID: <36ACE9EC.6B848566@w3.org>
To: olga <olga@goliath.eai.com>

olga wrote:

> I am not using the HTCacheFilter and instead add the header HT_C_IMS (If-
> modified-since) to the GET request. Often the header is not added because the
> Last-modified field in anchor is parsed to a negative value. Why is that
> happening?

Unless there is something wrong in the date parser (or the format) then
it is because it doesn't have a LM date and hence it returns -1. What
the persistent cache allows you to do is to use etags instead and to
maintain these etags persistently so that you can start the app at a
later time and still be able to use conditional GET requests.
> Also even if Last-modified is parsed to positive value, and If-modified-since
> is added to headers the file is still loaded from server and 200 is returned.

If the server sends back a 200 then it is because it thinks that the
document has changed.

Is there any reason why you can't use the normal libwww persistent
cache? Amaya, Web Commander, and the webbot are all using it.


Henrik Frystyk Nielsen,
World Wide Web Consortium
Received on Monday, 25 January 1999 17:02:29 UTC

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