scope of the appcache

In http://www.w3.org/TR/2011/WD-html5-20110525/offline.html#appcache
Nothing is said about the intended scope of the appcache, can it be 
implemented as being system-wide? (and in that case quid of 
user-authenticated informations).
Thanks,

-- 
Baroula que barouleras, au tiéu toujou t'entourneras.

         ~~Yves