Re: Logic Bag concerns

    I would also vote for an opaque cache validator.  We would need an
    "If-cache-valid: <validator> " and an "If-cache-stale: <validator>"
    and we would need to specify their *semantics*.  E.g. for a Range:
    request with an If-cache-valid header send the range if valid, else
    send entire document.
    
Can you explain why we need both
	If-cache-valid: <validator>
and
	If-cache-stale: <validator>
instead of simply
	Cache-validator: <validator>
along with a set of rules that explain how it is supposed to
be interpreted?

E.g., for
	GET
	Range: 3-8
	Cache-validator: XYZZY
I would expect the semantics to be
	if the validator of the actual object is XYZZY then
	return range 3-8, else return the whole thing

You might argue that one could use:
	GET
	Range: 3-8
	If-cache-stale: XYZZY
but this seems to mean
	if the validator of the actual object is NOT XYZZY then
	return range 3-8, else return nothing
but that doesn't make a lot of sense to me, because I don't think
it is rational to obtain a range of bytes if your cached copy
of the entire document is known to be invalid.

-Jeff