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Re: ACTION-308 (part 2) Updates to 'The Self-Describing Web'

From: <noah_mendelsohn@us.ibm.com>
Date: Thu, 7 Jan 2010 17:21:46 -0500
To: John Kemp <john@jkemp.net>
Cc: Larry Masinter <masinter@adobe.com>, "www-tag@w3.org WG" <www-tag@w3.org>
Message-ID: <OF96D52F36.C8AD75B7-ON852576A4.0078905E-852576A4.007A806C@lotus.com>
John Kemp wrote:

> On Jan 6, 2010, at 4:52 PM, noah_mendelsohn@us.ibm.com wrote:
> 
> [...]
> 
> > Furthermore, the draft text really doesn't explain how allowance for 
> > sniffing would change the rest of the SDW story.
> 
> And that was deliberate. I am not "allowing sniffing" so much 
> as saying, "if you are going to sniff then do it this way". I 
> didn't intend to change the meaning of the SDW story at all, or
> its relationship to the use of authoritative metadata.

I know, but that's what I'm unhappy about.  I think that once we even 
bring up the possibility, we should explain the implications. 

Your draft text is:

<original>
As noted above, and for other reasons (such as content aggregation), it 
may not be possible for a browser to reliably determine, via inspection of 
a Content-Type HTTP header or other external metadata alone, the intended 
interpretation of Web content. In such cases, a browser may inspect the 
content directly (commonly known as "sniffing"). The consequences of such 
an action are described in [AuthoritativeMetadata]. In particular, 
sniffing Web content should only be done using an accepted and secure 
algorithm, such as [BarthSniff].
</original>

I would probably be happier with something close too:

<proposed>
For the Web to have the desirable properties described in this finding, 
it's essential that content be served with a media-type that correctly 
labels its content, and likewise it's essential that user agents such as 
browsers interpret the received data per the specifications for that 
media-type.
Unfortunately, there are many servers on the Web that are not properly 
configured, and which serve incorrect Content-types.  In particular,
content intended to be interpreted as text/html, image/jpeg or other 
common types is sometimes served as text/plain.
Such incorrect labeling of content is contrary to Web architecture, and it 
undermines many of the valuable Web characteristics described by this 
finding.

Nonetheless, in part because such mislabeled content is common, certain 
browsers and other user agents have been coded to guess or "sniff" the 
intended content type, particularly for responses that are explicitly 
typed as text/plain.  Such sniffing breaks the chain of accountability 
described in this finding, making it more difficult for a user to hold the 
publisher responsible for a document's contents.

Other negative consequences of sniffing are described in the 
[AuthoritativeMetadata].  For example, "sniffing" can also expose the user 
agent to security vulnerabilities;  these can to some degree be minimized 
by using more secure algorithms, such as the ones described in 
[BarthSniff].
</proposed>

This might actually go in as a new, short Chapter 7 in SDW, I think.  That 
would bump the conclusions section to become #8.


> >  After all, we give 
> > examples in which providers of data are held legally accountable for 
> > having published certain content, precisely because the chain
> of normative 
> > specifications makes clear their correct interpretation.  In 
> a world where 
> > people start to "sniff", am I accountable for the (mis) 
> interpretation of 
> > something served as text/plain that just happens to resemble 
> some other 
> > media type?  The whole point of SDW is to tell stories like that.
> > 
> > So, I agree with Larry that we should steer clear of 
> elevating sniffing to 
> > being even a good practice at the architecture level (it's not a 
> > "principle" in the sense of AWWW principles in any case); 
> even if we do 
> > want to acknowledge that widespread use of sniffing in practice in a 
> > revised SDW, I think it behooves us to carefully explain how the core 
> > stories about accountability and lack of ambiguity are affected.
> 
> I agree that it would be good to explain the ambiguity 
> introduced by sniffing.

See above for a rough proposal
 
> >  I think 
> > we have two choices:  1) leave SDW alone -- it tells a quite coherent 
> > story at the architecture level, and we can view instances of
> sniffing as 
> > deviations from the architecture
> > or 2) do a very careful job of explaining 
> > just what does and doesn't change in the SDW story given thatsniffing 
> > happens.
> 
> I have roughly attempted your choice 1) with the understanding 
> that this was the will of the group. As you note though, we 
> could do a much more careful job of explaining what changes 
> given that sniffing happens.
> 
> Regards,
> 
> - johnk
--------------------------------------
Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
--------------------------------------








John Kemp <john@jkemp.net>
Sent by: www-tag-request@w3.org
01/07/2010 10:15 AM
 
        To:     noah_mendelsohn@us.ibm.com
        cc:     Larry Masinter <masinter@adobe.com>, "www-tag@w3.org WG" 
<www-tag@w3.org>
        Subject:        Re: ACTION-308 (part 2) Updates to 'The 
Self-Describing Web'



On Jan 6, 2010, at 4:52 PM, noah_mendelsohn@us.ibm.com wrote:

[...]

> Furthermore, the draft text really doesn't explain how allowance for 
> sniffing would change the rest of the SDW story.

And that was deliberate. I am not "allowing sniffing" so much as saying, 
"if you are going to sniff then do it this way". I didn't intend to change 
the meaning of the SDW story at all, or its relationship to the use of 
authoritative metadata.

>  After all, we give 
> examples in which providers of data are held legally accountable for 
> having published certain content, precisely because the chain of 
normative 
> specifications makes clear their correct interpretation.  In a world 
where 
> people start to "sniff", am I accountable for the (mis) interpretation 
of 
> something served as text/plain that just happens to resemble some other 
> media type?  The whole point of SDW is to tell stories like that.
> 
> So, I agree with Larry that we should steer clear of elevating sniffing 
to 
> being even a good practice at the architecture level (it's not a 
> "principle" in the sense of AWWW principles in any case);  even if we do 

> want to acknowledge that widespread use of sniffing in practice in a 
> revised SDW, I think it behooves us to carefully explain how the core 
> stories about accountability and lack of ambiguity are affected.

I agree that it would be good to explain the ambiguity introduced by 
sniffing.

>  I think 
> we have two choices:  1) leave SDW alone -- it tells a quite coherent 
> story at the architecture level, and we can view instances of sniffing 
as 
> deviations from the architecture
> or 2) do a very careful job of explaining 
> just what does and doesn't change in the SDW story given that sniffing 
> happens.

I have roughly attempted your choice 1) with the understanding that this 
was the will of the group. As you note though, we could do a much more 
careful job of explaining what changes given that sniffing happens.

Regards,

- johnk

> 
> Noah
> 
> --------------------------------------
> Noah Mendelsohn 
> IBM Corporation
> One Rogers Street
> Cambridge, MA 02142
> 1-617-693-4036
> --------------------------------------
> 
> 
> 
> 
> 
Received on Thursday, 7 January 2010 22:19:40 GMT

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