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

From: Tantek Çelik <tantek@cs.stanford.edu>
Date: Sun, 16 Jun 2002 21:43:58 -0700
To: Etan Wexler <ewexler@stickdog.com>, www-style@w3.org
Message-id: <B932B71D.E60A%tantek@cs.stanford.edu>

On 6/14/02 1:19 PM, "Etan Wexler" <ewexler@stickdog.com> wrote:

> 
> 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.

The determination may be trivial to those well versed in the language of the
specification, however using the term 'declaration' is still an additional
level of semantic separation that is unnecessary.  Thus it makes more sense
purely for readability (nevermind that more authors know the term "property"
than the term "declaration") to directly use the term 'property' as the text
does currently.


>>> "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?

 http://www.w3.org/TR/REC-CSS2/grammar.html


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

The above-mentioned grammar uses the production "ruleset" to refer to what
in the prose of the specification is called a "rule".


> 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.

There are at least two examples of rules that only apply to particular media
types:

1. @page only applies to page media.

2. @media foo { ... } only applies to media foo, where foo is one of the
valid media types as defined in CSS2.


>> The HTML4 model of alternate style sheets was updated in and superceded by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 reference is in my next statement which you quoted:

>> 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.

If there had been a change there would be a need to say why.  There is no
need to justify use of what is already there, other than perhaps "because it
is in a W3C REC".


>> Similarly, the CSS Mobile Profile has the same wording.
> 
> Well, if need be, change that, too.

Sounds like you are requesting a change in CSS in general (that is, a change
in CSS TV Profile, a change in CSS Mobile Profile, and potentially a change
in CSS2 (which would likely be need to be made in CSS2.1)).

I am not opposed to this change per se, however I believe it to be outside
the scope of the CSS TV Profile.

If you wish to pursue this change, I ask that you propose it as a change (in
a separate email) to CSS2 to be then adopted by other specifications which
depend or reference CSS2.

For my part, I will take your proposal (once posted) and put it on the
agenda for the next CSS working group teleconference so that the group may
discuss your proposal and move forward accordingly.


>>> "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?

From a specification standpoint, yes.

> Is it possible 
> to change wordings in the CSS TV Profile and, by way of CSS2.1, in level 2?

Yes, this would be possible too - and that is what I am suggesting you ask
for above.  


> 
>> And again, CSS Mobile Profile has the same wording.
> 
> As the CSS Mobile Profile has yet to reach Recommendation and is open to
> change,

It has however reached Candidate Recommendation, and the changes that can
occur during CR are much more restricted.  It will be up to the group to
decide if the change you propose can be accepted during CR.

> I 
> see no reason to let its wording dictate the wording of the CSS TV Profile.

Again, consistency.  There is no reason for CSS TV Profile to break from
CSS2 or CSS Mobile Profile in this way.  There is at least one good reason
to keep it consistent however, and that is that an implementation
implementing both should not have to be different in this way.



>> 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.

This kind of wordsmithing has introduced bugs into the specifications in the
past - for that reason alone it is best to avoid this practice.

And anytime I have seen a change introduce to wording in a spec which is
intended to have no semantic difference, I have seen many many authors,
developers, programmers spend hours of time trying to divine _why_ the
change was made, and assuming that because the change was made there _must_
be something subtly different being implied, and go to all sorts of
contortions of logic to justify a difference in implementation however
small.  

Your argument for clarity is strongly outweighed by the amount of time
wasted by many many individuals as a result of reading the before/after
wordsmithed text.


>>> "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.

The advantage is that authors _understand_ the term "properties" much more
so than "declarations".

Readability is important - authors already complain that W3C specs are
difficult to read because of their spec-ese, let's not make it any worse
than it needs to be.


>>> 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.

Agreed.


>>> '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?

It is not an all or nothing situation.  Typically, there is some ability to
specify fonts - just not nearly enough to imply the level of control implied
by the abovementioned 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.

It is no worse than CSS2 or CSS1 for that matter, yet this [questions about
character encoding schemes] doesn't appear to have been an obstacle for the
implementation or wide adoption of CSS.

If you think this is something that could be improved in CSS2 (perhaps for a
CSS2.1), I recommend that you propose it as such.

Thanks again for the additional well thought out thorough feedback Etan.  I
believe all the issues you mentioned which were germane to the CSS TV
Profile have been resolved, and that the CR draft will benefit from the
input you have provided.

Tantek
Received on Monday, 17 June 2002 00:37:48 GMT

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