[Bug 14702] appcache: always up-to-date applications

https://www.w3.org/Bugs/Public/show_bug.cgi?id=14702

--- Comment #16 from Ian 'Hixie' Hickson <ian@hixie.ch> 2011-12-02 03:29:53 UTC ---
(In reply to comment #15)
> 
> Now say that facebook wants to "enable offline". If they simply add a manifest
> to all pages that they want to offline, this means that when the user goes to
> facebook the first time in the morning, he/she will see the appcache-cached
> version, not the one from the network.

No, what they do is they separate the content of the pages from the data in the
pages, and they fetch the data on page load.


> This is not acceptable for this use case. While it's an improvement in
> performance, it's a degradation in user experience since the user will see an
> outdated version of the website.

No, the data will be fetched as soon as the page loads and thus will appear
just as fast as it would if there was no appcache at all, except the page
itself will load faster (only the data has to be downloaded, not all the
supporting app code).


> For facebook to continue to "work", they have to create a whole new set of URLs
> which are only used for the offline version of the website.

No, they just use the same pages.


> To fix this, I propose that we change the semantics such that if the UA is
> online, the UA is instructed to only use the appcache *after having checked
> that the cached version is up-to-date*.

Then you lose the entire performance benefit of appcache, which is that you can
run the app immediately without any network latency.



As far as I can tell, the use case for the feature being discussed here is that
authors want to be able to author pages where:
 - for users who go to a page for the first time, the page loads as now,
without any appcache stuff.
 - for users who go to the page again, the UA somehow checks with the server as
it is loading the page to get a list of which of the resources that are already
cached for the page can be kept as is and which need to be fetched afresh.
 - for users who go to the page again while the page returns a result other
than 200, 404, or 410, the UA just uses the old page, the same way appcache
works today.

Is that right?

We can certainly support this use case, but it's not at all obvious that any of
the proposals that have been made so far actually achieve this.

-- 
Configure bugmail: https://www.w3.org/Bugs/Public/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the QA contact for the bug.

Received on Friday, 2 December 2011 03:30:01 UTC