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Re: [CSS21] Section 6.1.3

From: Craig Northway <craign@cisra.canon.com.au>
Date: Thu, 25 Aug 2005 18:03:58 +0200
Message-ID: <430DEBEE.3090905@cisra.canon.com.au>
To: Ian Hickson <ian@hixie.ch>
Cc: www-style@w3.org

Hi,

Ian Hickson wrote:

>On Thu, 25 Aug 2005, Craig Northway wrote:
>  
>
>>>No, it's not optional, but that is because section 3.2 requires that 
>>>user agents implement CSS consistent with the descriptions laid out in 
>>>the spec, including section 6.
>>>      
>>>
>>I do not think this is clear enough. I think that each statement 
>>throughout the specification that requires conformance from a user agent 
>>should use terminology that indicates this.
>>    
>>
>
>This is the case.
>
>CSS is not defined in terms of functional steps ("do this then do this 
>then do this"), it is defined in terms of a model ("it is this"), an 
>implementation for which must then be found.
>  
>
The example I quote from section 6.1.2 and 6.1.3 appear to be a 
functional steps in the model.

>Most of the CSS spec describes the model. The only thing a UA implementor 
>has to do to claim conformance is be consistent with the model.
>
>
>  
>
>>The QA Framework: Specification Guidelines
>>(http://www.w3.org/TR/2005/REC-qaframe-spec-20050817) requirement 7 states:
>>
>>         Use a consistent style for conformance requirements and
>>         explain how to distinguish them
>>
>>Requirement 8 states:
>>
>>         Indicate which conformance requirements are mandatory, which
>>         are recommended, and which are optional.
>>
>>Specifying in section 3.2 that a UA must conform with the rest of the 
>>specification does not make it easy to distinguish conformance 
>>requirements. Nor does it make it easy to determine which comments are 
>>mandatory, recommended or optional.
>>    
>>
>
>It should be pretty clear; if something describes the model, it's 
>something the implementation has to be consistent with.
>
How do I know precisely what is defining the model? Parts of the model 
that must be performed should be expressed using 'must' or 'shall' or 
other suitable terms.

> Certain things are 
>explicitly stated as being outside the model ("The behavior of the 'auto' 
>value is user agent-dependent") and RFC2119 terms are used when 
>conformance criteria outside the model are required ("but should cause a 
>scrolling mechanism to be provided for overflowing boxes")
>
But, everything that may be in the model is not obvious.

>  
>
>>>Specifically, in the case of 6.1.3, the two "must" requirements that 
>>>apply are "For each element in a document tree, it must assign a value 
>>>for every applicable property according to the property's definition 
>>>and the rules of cascading and inheritance" and "A user agent that 
>>>renders a document with associated style sheets must respect points 
>>>1-5 and render the document according to the media-specific 
>>>requirements set forth in this specification", which are list item 4 
>>>and the third bullet point in section 3.2 respectively.
>>>
>>>Please let us know if that addresses your concern.
>>>      
>>>
>>Where are these musts you indicate that apply to section 6.1.3? they 
>>are not linked to section 6.1.3.
>>    
>>
>
>Section 3.2.
>
>If this does not address your concern please explain how the CSS spec 
>should be rewritten to use a different conformance model.
>
Each statement that is required to be peformed by the UA in implementing 
the model should be specified with must or shall.

> It is not clear 
>to me how we can require conformance to a model without using the 
>mechanism used by CSS2.1. For example, take margin collapsing:
>
>   http://www.w3.org/TR/CSS21/box.html#collapsing-margins
>  
>
I fail to see how this is relevant to my initial comment.

Regards,
Craig Northway
Received on Thursday, 25 August 2005 16:04:14 GMT

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