Another thought, regarding this...
Have unique URLS won't stop IE's aggressive caching of images though. A lot
of my caching problems are not the HTML code but images that are cached by IE.
For example, a recent problem which still has me stumped is the case of an
admin system which includes a file upload process.
The process entails a particular file being uploaded (say emu.jpg) and then
referenced by the following page (ie ubuys/emu.jpg) to display that the
image was successfully loaded. However, if the image changes, though the
reference stays the same, the old image will still show, or if there now is
no image, IE still shows that there is an image. Accordingly the admin
system is now "lying" to the administrators and they don't know what to
believe.
Any ideas on how to get around this?
Garth
At 11:25 22/07/02 -0700, you wrote:
>Good point, Robert .... always thinking ..
>
>Ian
>
>-----Original Message-----
>From: Robert Shubert
>
>Just an interesting note:
>
>The HASH function of T2K restricts output to 32 characters and it is
>therefore possible to create two identical HASHes with <@CIPHER
>action=hash str=<@CURRENTTIME>>.
>
>Another way of creating an ever increasing value is <@TSTOSECS
><@CURRENTTIMESTAMP>><@TIMER> This value is ensured to be unique unless
>the same person is able to retrieve two pages in the same millisecond.
>Keep in mind that this only works if the CURRENTTIMESTAMP is ever
>increasing, if you adjust the time on the server (or adjust for daylight
>savings) it could create duplication, although it's still highly
>unlikely.
>
>Bob Shubert
>Tronics
>
> > Ian Daniel wrote:
> >
> > Hey Garth:
> >
> > We experienced great caching issues which would not all be solved
> > using the approach described below. Remember that cache involves
> > multiple versions and schemes of browsers, proxy servers, firewalls,
> > network routers and servers.
> >
> > In my experience, the only way to "beat them all" in one action is to
> > ensure that every URL is unique.
> >
> > For dynamically-generated pages, we append what we call a "no-cache"
> > argument to every URL. At NCOL, we have standardized on a hash of the
> > currenttimestamp, like so:
> >
> > &_nc=<@CIPHER action=hash str=<@CURRENTTIME>>
> >
> > For statically-generated pages, we add a large random number,
> > generated in JavaScript, to ensure that every browser display (even
> > those presented by the browser back button) has a unique URL. There
> > are several ways to do this. We usually use:
> >
> > <script language="javascript">document.write('<a href="whatever.taf?'
> > + Math.round(Math.random()*1000000000) + '">Your Link
> > Here</a>')</script>
>
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