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Issue 535 - viewing state for things removed from cache

From: Charles McCathieNevile <charles@w3.org>
Date: Wed, 10 Apr 2002 16:46:36 -0400 (EDT)
To: WAI UA group <w3c-wai-ua@w3.org>
Message-ID: <Pine.LNX.4.30.0204101639410.28193-100000@tux.w3.org>
I disagree withthe proposed resolution of issue 535. This is not really
really simple, but I don't think it is really really complex either...

A page may not be placed in the cache for a number of reasons. In the real
world there are pages that actually change, so are not listed as cacheable
and pages that do not change, but are served as nucacheable for no better
reason than the site developer didn't bother changing the server default

Browsers often cache pages anyway, for things like offline browsing, and may
decide not to cache a page according to more or less any criteria at all.

So if a browser keeps a history, it should be able to get the page and be
where one was when one left, if the page has not changed - as determined by
the HTTP headers, or by the browser doing a diff against its cache for any
developer who is really not very trusting and likes that much work.

If the page has changed, then it may not make much sense to keep the required
information, since the user may need to know what has changed.

(there is an implementation issue of how much history and how much point of
regard information should be kept - if there are 1000 pages in the history,
which is what I like to keep, does it need to cover all of them, or is it OK
to only keep it for the last 100?)



the Issues list includes the following:

 Issue 535 (Second Candidate Recommendation): 9.4 (restore history): Must
consider UA cache availability
          Name: Tantek Celik
          Source URL:
          Date: Wed Apr 10 10:45:11 2002
          Category of issue: Orientation
          Type of issue: Checkpoints
          Resolution summary: Not resolved
          Resolution URL: Not resolved
          First working draft: No reference
          The checkpoint reads:

          "For user agents that implement a viewport history mechanism, for
each state in a viewport's browsing history, maintain information about the
          of regard, content focus, and selection."

          However, even when a user agent implements a history mechanism, it
may not keep all pages in its cache.

          Proposal: Do not require the user agent to restore state variables
for pages removed from the history cache.

Charles McCathieNevile    http://www.w3.org/People/Charles  phone: +61 409 134 136
W3C Web Accessibility Initiative     http://www.w3.org/WAI  fax: +33 4 92 38 78 22
Location: 21 Mitchell street FOOTSCRAY Vic 3011, Australia
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Received on Wednesday, 10 April 2002 16:46:36 UTC

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