[Fwd: Re: Subgroup to handle semantics of HTTP etc?]

This is a copy of Noah's message.  I forgot to reply all and Noah 
thought I want to communicate in private and kindly responded me in 
private too.

attached mail follows:

Xiaoshu Wang writes:

> Honestly, after httpRange-14, I don't think that many people will 
> consider it O.K. to 200 back a "clock" anymore.

That's an interesting question.  How about if, instead of a clock, I said 
the resource was "the current time in Boston"?  The current time in Boston 
can be quite well conveyed in a message, I'd think, yet clearly there will 
be different representations at different times.

> I think from this wording in AWWW - "The distinguishing characteristic 
> of these resources is that all of their essential characteristics can be 

> conveyed in a message", the implication, at least for me, is that "from 
> the representation of an information resource, we can *fully* understand 

> the resource".

No.  It says that if you wanted to, you could come up with a message that 
would convey the essential characteristics.  It doesn't, at least in the 
statement you quote, say the every representation must do that.  I think 
we agree that negotiation is allowed based on language, say French and 
English.  Let's assume that there is a press release written originally in 
French, and translated into English to support access by both French and 
English speaking readers.  Surely we don't think that the back translation 
from English to French is unambiguous.  So, I've shown by at least that 
counter example that, although the press release is well representable in 
a message, not every good representation must suffice for fully 
reconstructing the resource.  Now, you used the words *fully understand*, 
and I confess I find them a bit ambiguous, but if you meant fully 
reconstruct, I don't think the quote from WebArch requires that.

Now, I've never believed in the superiority of the current 200 semantics 
to the degree that, say, Tim appears to.  I don't see why the Web would 
have crumbled if 200 had instead been defined as:  I'm giving you some 
'representation' that will at least vaguely remind you of the resource, so 
by all means return a 200 for a human being and when you send along her 
picture!'  Still, we're down the road with a different definition for 200, 
and I don't propose to change it.  I admit that it's a little incongruous 
to say '200 is only acceptable if you could have given a full fidelity 
representation of an object, but it doesn't mean that in this particular 
case you have done so!'  Nonetheless, that's my understanding of the 
current design.  For better or worse, it allows you to infer from the 
status code something about the nature of the underlying resource.

BTW:  I see you replied to me in private and I am answering in kind.  You 
have my permission to post this correspondence to www-tag should you wish 
to.  Thank you.

Noah

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Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
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