It's not clear to me from the descriptions of the cache manifest that I've read (e.g. http://www.w3.org/TR/offline-webapps/#offline and elsewhere) what this file does. I'll explain what I find to be unclear.
The heading name ("Offline Web Applications") suggests that the cache manifest is relevant only for offline scenarios; the cache manifest is defined as
"The mechanism for ensuring Web applications are available
even when the user is not connected to their network"
But does the cache-manifest have any implications for online use? It seems so. The file contains a NETWORK section, and the files listed there (sometimes I've seen it described as the last file listed there) do not go into the cache; they
"...should never be cached, so that any attempt to access that file will bypass the cache."
What would "bypass the cache" mean in an offline context? But if the user is online, are files listed in the NETWORK section always obtained from the server, even if they had been previously cached?
The files added to the NETWORK section are said to be "white-listed". Normally, to whitelist something means to allow it. Actually, these files are being black-listed -- i.e. not allowed into the cache.
This page is being copied verbatim or paraphrased lemming-like in many other documents, so the original's imperfect clarity is being perpetuated.
So, my question: could someone please provide an authoritative, clear, and concise definition of the purposes the cache-manifest serves, giving examples of how one would set cache-expiration policies, such as expiring content at midnight on December 31, 2010. Is future-expiration even possible to do, declaratively, in HTML5?
Thanks