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Re: Revisiting Authoritative Metadata (was: The failure of Appendix C as a transition technique)

From: Robin Berjon <robin@w3.org>
Date: Mon, 25 Feb 2013 13:56:20 +0100
Message-ID: <512B5F74.4010500@w3.org>
To: "Eric J. Bowman" <eric@bisonsystems.net>
CC: Larry Masinter <masinter@adobe.com>, Henri Sivonen <hsivonen@iki.fi>, "www-tag@w3.org List" <www-tag@w3.org>
On 24/02/2013 20:20 , Eric J. Bowman wrote:
> Robin Berjon wrote:
>> I would support the TAG revisiting the topic of Authoritative
>> Metadata, but with a view on pointing out that it is an architectural
>> antipattern. Information that is essential and authoritative about
>> the processing of a payload should be part of the payload and not
>> external to it. Anything else is brittle and leads to breakage.
>
> Antipattern?  This *is* the architecture.

I beg to differ. That's hardly an argument is it? :)

> Unlike FTP, the HTTP and
> Gopher protocols introduced the notion of sender intent

Which is good because:

[list use cases here]

The trade-offs involved are positive because:

[discussion of why sender-intent is good]

Seriously, I have looked, yet I can't find a single piece of 
justification for the Sender Intent Dogma that doesn't involve hand 
waving and the same example practically pasted in over and over again.

I would presume that sender intent, if valuable, would be informative at 
best. User intent trumps all.

> Unlike
> Gopher, HTTP re-used MIME, avoiding the requirement of versioning the
> protocol every time a new format (which may have use beyond the Web) is
> introduced ('h=html' is widely implemented in Gopher, not specc'd).

Well, given a choice that's certainly a good thing (but entirely 
orthogonal).

> Expressed formally, this "late binding of resource to representation" is
> fundamental to Web architecture; its implementation in HTTP is the
> Content-Type header.  Without it, there is no mechanism to express
> sender intent, even one that's somewhat ignored in practice.  I won't
> equivocate on thinking this to be a good thing...

Again, we give such prominence to sender intent, despite obvious 
wide-scale deployment issues, because [blank].

> Given any architecture which supports a variety of data formats, if
> intermediaries are to be allowed to participate, they can't be required
> to decode (sniff) the payload to determine the format anyway, without
> requiring them to have high-end CPUs.  As it is, the Web scales nicely,
> right down to my decade-old desktop embedded-Linux squid router.

But intermediaries that do that will be making the wrong decision on a 
very regular basis.

> The alternative to Authoritative Metadata, is for the TAG to deprecate
> sender intent altogether; iow, redefine what Web architecture *is*.

If the TAG can't redefine Web architecture (in this instance I would say 
"properly define"), what is it for?

When you note that a system of rules is broken (and I think that the 
fact that we need a sniffing document demonstrates that very clearly) 
you can do one of two things:

 Ask that people "behave better" and go against their best interest 
(this works, why bother fixing it?).
 Fix the rules.

Unless you have the means to enforce strong ethical standards, I know of 
no case in which the former approach actually works.

-- 
Robin Berjon - http://berjon.com/ - @robinberjon
Received on Monday, 25 February 2013 12:56:32 GMT

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