HTML5 deployment: progress comes into sight

[Roland Huettmann]

@BR wrote: ... "What's very difficult, as you write in detail, are
"callbacks" for _synchronous_communication..."

Callback functions?

In my mind, a "callback" is always asynchronous -? Let us say in Javascript
- passing the function name and parameters of Javascript through LCS/LCB
and then somehow the result is put into a variable while I am continuing
processing other stuff. Maybe I am wrong? I am calling a server, waiting
for the result, but I could wait forever and the result will possibly never
come. So it would be blocking doing other things. A callback would free me
from waiting for nothing. Is this a right definition for "callback"?

What defines "callback"? I could understand though that I am calling a
function in the browser widget (using the "callback" name of the function)
which will be executed through Javascript and will be returning a value for
further processing. What means "synchronous" or "asynchronous" in this
context?

Again, in my mind, a callback is when I send off a parcel to my friend with
an instruction to tell me that it arrived and the confirmation of arrival.
The confirmation is the callback. Then I know my friend received the
parcel. Or in another analogy, I am calling someone by phone asking to call
me back. The person may call immediately or may call never or in a couple
of days. This is asynchronous.

How would a callback become synchronous? Is it then still a "callback"?