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[css3-syntax] [css3-speech] normative media types, mutual-exclusivity

From: Daniel Weck <daniel.weck@gmail.com>
Date: Fri, 10 Dec 2010 18:44:51 +0000
Message-Id: <9B275F66-BA8B-4F05-8F37-E9303ED68967@gmail.com>
To: www-style@w3.org
Hi all,
I am in the process of completing a review of the CSS3 Speech Module  
and its related dependencies, and I came across general statements  
that seems ambiguous to me. Please correct me if I'm wrong.

In section "7.1.4. Recognized media types" of the CSS-Syntax  
specification [1], the following normative statement is pretty clear  
(note the "MUST"):

"A CSS media type names a set of CSS properties. A user agent that  
claims to support a media type by name must implement all of the  
properties that apply to that media type. ... The names of media types  
are normative."

So for example, let's take the CSS-Speech Module [2]: conforming user  
agents (e.g. web-browsers with screen-reader support) must implements  
all of the CSS Properties marked with the "speech" media type. To me,  
this means that the "Media" field in the description of each CSS  
Property has a critical normative value: it is the only way for  
implementors to know, without ambiguity, what properties MUST be  
handled in order to claim conformance as a user-agent supporting  
speech-synthesis.

The same remark obviously applies to any other CSS Property, for any  
other media type normatively specified in CSS3 (e.g. visual, braille,  
print, etc.).

Yet, in the same section "7.1.4" we read:

"the 'Media' field in the description of each property is informative."

I would have thought that this should be "normative", not  
"informative". Could one of the CSS-Syntax editors please clarify this ?

Additionally, section "7.1.4" also states:

"Media types are mutually exclusive in the sense that a user agent can  
only support one media type when rendering a document."

This statement is not problematic in itself, but section "2.  
Introduction" of the CSS-Speech Module seems to be make a  
contradictory assertion:

"Style sheet properties for text to speech may be used together with  
visual properties (mixed media)"

Any thoughts ?

Thank you :)
Regards, Daniel

[1]
http://www.w3.org/TR/css3-syntax/#media

[2]
http://www.w3.org/TR/css3-speech/#property-index
Received on Friday, 10 December 2010 18:45:26 GMT

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