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Re: LC-2067: Conformance statement - MUST and SHOULD

From: Jo Rabin <jrabin@mtld.mobi>
Date: Fri, 12 Sep 2008 16:30:23 +0100
Message-ID: <48CA8B0F.5080206@mtld.mobi>
To: Francois Daoust <fd@w3.org>
CC: public-bpwg-ct <public-bpwg-ct@w3.org>

Agree strongly with this. I think for the sake of clarity it might be 
worth pointing out that that an explanation for non conformance with the 
SHOULDs needs to identify why a deployment is different from the norm, 
rather then "we didn't feel like it", "our product manager told us not 
to" and I think it should be clear that conforming implementations don't 
follow the SHOULDs only in specific exceptional circumstances.

As to where such a conformance statement might be lodged - send to 
fd@w3.org? :-)

Jo

On 12/09/2008 14:54, Francois Daoust wrote:
> 
> The Last Call comment:
> http://www.w3.org/2006/02/lc-comments-tracker/37584/WD-ct-guidelines-20080801/2067 
> 
> 
> As text:
> "* Section 3.4 / 3.5 "A [Content|Transformation] Deployment conforms to
> these guidelines if it follows the statements..."  What does "follows"
> mean here -- if they conform to all MUST level requirements? SHOULD
> and MUST?"
> 
> Indeed, the more precise we are in the Conformance section, the better.
> 
> Conformance to MUST is implied, but we'd better write it down explicitly 
> anyway.
> 
> Conformance to SHOULD must be stated, because different specifications 
> use SHOULD (or equivalent) differently. For instance:
> - QA Framework Specification Guidelines - SHOULD statements are totally 
> optional
>   [[ Good Practices use the same imperative voice, but are optional. 
> They are equivalent to SHOULD or RECOMMENDED statements in the RFC2119 
> style. Their implementation or non-implementation does not affect 
> conformance ]]
>    http://www.w3.org/TR/qaframe-spec/#conformance-criteria
> 
> - Web Security Context: User Interface Guidelines - SHOULD statements 
> define a second conformance level
>  [[ A user agent conforms to this specification at the [Definition: 
> basic level] if it honors all MUST and MUST NOT clauses of this 
> specification.
>  A user agent conforms to this specification at the [Definition: 
> advanced level] if it also honors all SHOULD and SHOULD NOT clauses of 
> this specification. ]]
>   http://www.w3.org/TR/2008/WD-wsc-ui-20080724/#conformance-levels
> 
> We use them with a different meaning, closer to the definition of SHOULD 
> in RFC 2119: we know there are valid cases when our SHOULD statements 
> may not be followed and we expect conforming products will justify 
> themselves when not following them.
> 
> Given the number of comments received on section 4.1.5 Alteration of 
> HTTP Headers values that sound like "yeah, but that's only a SHOULD, 
> CT-proxies are free to do whatever they want", I think we could go even 
> further than just stating the above in the Conformance Section: we could 
> define an Implementation Conformance Statement (ICS) to be filled out by 
> products that want to claim conformance to the spec. See for instance:
>  * ICS for the above-mentioned QA Framework Specification Guidelines - 
> http://www.w3.org/TR/2005/REC-qaframe-spec-20050817/specgl-ics.html
>  * an example of ICS for WEBCGM: 
> http://www.sdicgm.com/cgmopen/sdi_print_master
> 
> The ICS would require justifications for the cases where SHOULD 
> statements are not followed, and although that involves more paperwork, 
> it seems to fit our case and needs. I would be happy to take an action 
> to dig into that direction and prepare a draft ICS, but I want us to 
> discuss that beforehand within the task force so that I don't start 
> working for nothing...
> 
> 
> In any case, I propose the following draft text to replace current 
> sections 3.4 and 3.5.
> 
> [[
> 3.4 Content Deployment Conformance
> 
> A Content Deployment conforms to these guidelines if it honors all MUST, 
> NUST NOT, SHOULD and SHOULD NOT statements in 4.2 Server Response to 
> Proxy. A Content Deployment that does not honor SHOULD and SHOULD NOT 
> statements in some cases MUST justify itself to claim conformance to 
> these guidelines.
> 
> 3.5 Transformation Deployment Conformance
> 
> A Transformation Deployment conforms to these guidelines if it honors 
> all MUST, MUST NOT, SHOULD and SHOULD NOT statements in 4.1 Proxy 
> Forwarding of Request, 4.3 Proxy Forwarding of Response to User Agent 
> and 5 Testing (Normative). A Transformation Deployment that does not 
> honor SHOULD and SHOULD NOT statements in some cases MUST justify itself 
> to claim conformance to these guidelines.
> ]]
> 
> 
> It's a bit clumsy, I should say, and my immediate reaction to my own 
> text is: yes, but where and to whom do they justify themselves? That 
> could be answered with an ICS, or with a lighter "Conformance claim" 
> section that would define a template claim.
> 
> Francois.
> 
Received on Friday, 12 September 2008 15:31:27 GMT

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