[whatwg] Application deployment

[Dave Singer]

At 21:45  -0700 29/07/08, Robert O'Callahan wrote:
>On Tue, Jul 29, 2008 at 11:20 AM, Dave Singer 
><<mailto:singer at apple.com>singer at apple.com> wrote:
>
>Caching is on a full URL basis, of course.  Once that is decided, 
>then yes, I think that pre-cached items for a given URL are in the 
>general cache for that site.
>
>
>A site that uses this feature is likely to be fragile. It will have 
>to have z.html both in the archive and available directly from the 
>server, in case z.html is requested before the load of the archive 
>has finished.

No.  The definition *for MPEG-21 files* (which is all I have 
specified so far) is that accesses to the matching absolute URL (or 
relative URL) from within the archibe MUST find the resource within 
the archive.  Since, as I say, this format starts with a directory, 
you know whether you have it or not.  If ZIP or JAR files don't have 
a directory, then yes, they have a different trade-off and must load 
the whole thing before they know.

You only need a resource *outside* the archive if it is requested 
'nakedly' from outside the archive.  If you do that, it might indeed 
hurt, but that's your choice as a site.

The performance trade-off is very simple;  if you have many small 
resources it may be much more efficient to ftch them as a package 
than individually.  The downside is that this is a single connection 
in a pre-defined order whereas multiple resources could be fetched on 
parallel connections, and as needed.  I doubt more connections to the 
same server gets you more bandwidth, however, and the mpeg-21 format 
also allows extent-based interleaving so that e.g. a lareg HTML page 
and and large JPEG can be loaded progressively together.

>And if those copies ever get out of sync you're in very big trouble, 
>because depending on the context, either the archive version or the 
>direct version is likely to consistently win the load race, so just 
>occasionally some clients will get the wrong version. This seems 
>like a highly error-prone design.
>
>Rob
>
>--
>"He was pierced for our transgressions, he was crushed for our 
>iniquities; the punishment that brought us peace was upon him, and 
>by his wounds we are healed. We all, like sheep, have gone astray, 
>each of us has turned to his own way; and the LORD has laid on him 
>the iniquity of us all." [Isaiah 53:5-6]


-- 
David Singer
Apple/QuickTime
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