[html5] Offline apps

Diane & Mike's Verizon Account dmrunels at verizon.net
Sat Apr 9 23:10:34 PDT 2011

I sure seem to see a Trojan horse here!

Sent from my iPhone

On Apr 10, 2011, at 2:03 AM, "Jukka K. Korpela" <jukka.k.korpela at kolumbus.fi> wrote:

> Ilkka Huotari wrote:
>> To summarize my ideas/problems so far:
>> - I would like to load certain pages from the web server when I'm
>> online (i.e. not from the cache).
>> - If I'm offline, I would like to load these same pages from the
>> cache.
> That's more or less what happens normally, though subject to caching conditions. The best approach to control such issues is via normal cache control, see http://www.mnot.net/cache_docs/
>> - Not sure if the above is supposed to be possible with the appcache
>> mechanism.
> No, the appcache mechanism is supposed to make an application work as if the user were offline, except that when he is actually online, the browser checks for the _cache manifest_ only (and if its contents has changed, the application cache is refreshed). It bypasses normal cache control, freshness information etc.
>> Problems:
>> - Pages are shown from the cache to user even when the user is online.
> So this works as defined.
>> This seems a bit unnecessary, especially if I have defined
>> "Cache-Control: no-cache" for the said pages.
> It's part of the idea of application cache. I wonder how useful the idea is... but in any case, it's not useful as a general replacement for normal caching.
> I wonder why you wish to defeat normal caching when the user is online, yet consider using an application cache. Preventing all caching of a resource normally makes sense only if the contents is automatically generated with unique data or updated by some automated process(es)  or otherwise very frequently (say, a news page), or something like that.
>> - Pages are cached/shown from the cache even if I put them into
>> network section. I really don't understand why, is this a bug in
>> browsers?
> Could be a bug. In my tests, application cache manifests haven't worked that perfectly, though in my early experiments, some oddities were caused by my mistakes. Browser tools for inspecting application caches seem incomplete - at some point, it seemed to be possible to see what happens, in Resources > Application Cache in debug mode in Google Chrome (the one you enter by right-clicking and selecting Inspect Element), but now it appears to be empty.
>> Also, the manifest file change isn't really solving these problems,
>> imo, because it means that multiple page page loads are needed until
>> the change is shown.
> By the current definition of application cache, changing the manifest contents (changing last write is enough - it's really a matter of contents matching, which is rather odd design, if you ask me) is the way to force browsers (when online) to refresh the application cache.
> -- 
> Yucca, http://www.cs.tut.fi/~jkorpela/ 
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