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Re: TV profile comments (WD-css-tv-20020515)

From: Etan Wexler <ewexler@stickdog.com>
Date: Fri, 14 Jun 2002 13:19:47 -0700
To: "Tantek Çelik" <tantek@cs.stanford.edu>, www-style@w3.org
Message-ID: <3D09ED73.22276.B086BE@localhost>
Message-ID: <CSS-TV-Profile-comments@d2002-06-14.etan.wexler>

Tantek Çelik responded to my comments on the CSS TV Profile 1.0:


> Each property in CSS2 defines whether or not it _applies_ to a particular
> media type (or set of media types).  No where is there any concept of a
> declaration as a whole applying to a specific media type or not.

A declaration only and always contains one property name, so the determination of 
whether the declaration applies to a medium is trivial.  If the named property applies to 
medium M, the declaration applies to medium M; otherwise, the declaration does not 
apply to medium M.

> > "TV-UA MUST ignore rules that apply to unsupported media types."
> > 
> > What does "rules" mean here?  It could mean at-rules, rule sets, at-rules
> > and rule sets, declarations, and more.
> 
> All forms of rules per the CSS grammar.

Which CSS grammar?  The CSS2 grammar defines a "statement" as either a rule set or 
at-rule.  Where is the term "rule" defined?

Anyway, how could a rule set apply to unsupported media types (or any media types)?  
To paraphrase, nowhere is there any concept of a rule set as a whole applying to a 
specific media type or not.

> The HTML4 model of alternate style sheets was updated in and superceded by
> CSS2.

Wow, that's a leap.  Where does CSS2 claim to update, much less supercede, HTML4's 
model of alternate style sheets?

> The text in the CSS TV Profile is derived from CSS2 Section 3.2
> subpoint 5.[2].

That subpoint comes after the notice, "This section defines conformance with the CSS2 
specification only. There may be other levels of CSS in the future that may require a 
user agent to implement a different set of features in order to conform."  You are saying 
that there has been a decision to stick to CSS2 wording, but not saying why.

> Similarly, the CSS Mobile Profile has the same wording.

Well, if need be, change that, too.

> > "Values MAY be approximated when required by the TV-UA."
> > 
> > For clarity, change to "A TV-UA MAY approximate computed values
> > when assigning actual values."
> 
> Again, this wording was taken from CSS2 Section 3.2, and I would like to
> keep it consistent.

Is keeping a specification consistently hazy better than clarifying matters?  Is it possible 
to change wordings in the CSS TV Profile and, by way of CSS2.1, in level 2?

> And again, CSS Mobile Profile has the same wording.

As the CSS Mobile Profile has yet to reach Recommendation and is open to change, I 
see no reason to let its wording dictate the wording of the CSS TV Profile.

> For clarity and [consistency] we should keep the same wording.

For clarity, we should choose the clearest wording, regardless of past wordings.  For 
consistency, we should stick to past wordings, regardless of clarity.  I choose clarity.

> > "Authors should be able to use style properties with an understanding
> > that the cascading rules are processed correctly"
> > 
> > Change "style properties" to "declarations".
> 
> AFAICT this does not semantically change the sentence.  Unless there is an
> advantage to the change, the wording should stay as is - this is another
> instance where CSS Mobile Profile has the same wording.

The advantage is that "declaration" is well defined, while "style property" is used here 
only.  The advantage is that authors write declarations, not properties.

> > 3. Selectors
> > 
> > Are the unsupported selectors to be parsed as
> > invalid (which would affect valid selectors in the same group)?
> 
> [Yes.]  The same as if a CSS1 UA were to encounter CSS2 selectors.

Please add a note explaining this effect.

> > 'font-size-
> > adjust', 'font-stretch', 'letter-spacing', 'text-shadow', 'Unicode-bidi', and
> >'word-spacing'
> 
> On set-top boxes, there are typically a very limited number of font choices
> (if even more than one).  It made more sense to leave out these properties
> rather than to tell people that they may (probably will) always revert to
> some initial setting due to platform constraints.

Given the limitations on fonts, why does the CSS TV Profile include any font properties?

> I hope my explanation helped at least a little.

Yes, thank you, it helped quite a lot.

> > What character encoding schemes are mandatory or suggested for
> > acceptance by a TV user agent?  What character encoding schemes are
> > mandatory or suggested for a TV Cascading Style Sheet?
[...]
> In short, the same as CSS2.

So there are no mandatory encoding schemes.  If I have a style sheet in UTF-8, I have 
no guarantee that a user agent conforming to the CSS TV Profile will accept the style 
sheet.  That saddens me.

-- 
Etan Wexler <mailto:ewexler@stickdog.com>
Received on Friday, 14 June 2002 16:16:56 GMT

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