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

The following are comments on the CSS TV profile working draft 
(<http://www.w3.org/TR/2002/WD-css-tv-20020515>).



The document lacks a summary of at-rule support.  A table for at-rules 
would be helpful.  As things stand, 'font-face', 'page', and 'color-profile' 
at-rules receive no mention.



2. Conformance


"If a TV-UA encounters a property that applies for a supported media 
type, the TV-UA MUST parse the value according to the property 
definition."

Change the first occurrence of "property" to "declaration".


"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.


"If the source document comes with alternate style sheets (such as with 
the "alternate" keyword in HTML 4.0 [HTML40]), the TV-UA SHOULD 
allow the user to select one from among these style sheets and apply 
the selected one."

Allowing just one style sheet at a time is more restrictive than the 
HTML4 model.  Change to "If the source document comes with alternate 
style sheets (such as with the "alternate" keyword in HTML 4.0 
[HTML40]), the TV-UA SHOULD allow the user to select from among 
these style sheets and apply the selected style sheets."


"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."


"Authors should be able to use style properties with an understanding 
that the cascading rules are processed correctly"

Change "style properties" to "declarations".


"A TV-UA that can process the 'run-in' value for the 'display' property will 
process the first display specification and then "write over" that value 
with the second display specification. A TV-UA that cannot process the 
'run-in' value will process the first display specification and ignore the 
second display specification."

The word "process" is too general and the word "specification" is but 
another way of writing "declaration".  Change to "A TV-UA that accepts 
the 'run-in' value for the 'display' property will accept the first 'display' 
declaration and then replace that declaration's value with the value from 
the second 'display' declaration. A TV-UA that does not accept the 'run-
in' value will accept the first 'display' declaration and ignore the second 
'display' declaration."



3. Selectors

Are the unsupported selectors to be parsed as valid but ignored during 
property assignment?  Are the unsupported selectors to be parsed as 
invalid (which would affect valid selectors in the same group)?

All pseudo-elements are missing from the table.

I ask for another column in the table to provide a rationale for the 
rejection of selectors.  The rejection of the 'hover' pseudo-class is 
obvious to me (television sets have no hovering cursor) but the other 
rejections are far from obvious.

4. Properties

Again, rationale columns would be most helpful.  The Working Group 
has decided to cast television as a visual-only medium, so the rejection 
of aural properties is obvious.  Apparently, television may decline to 
support tables and generated content, which, though a choice requiring 
its own explanation, provides a rationale for many of the remaining 
property rejections.

However, properties like 'background-attachment', 'direction', 'font-size-
adjust', 'font-stretch', 'letter-spacing', the 'max' and 'min' dimensions, 
'overflow', 'text-shadow', 'Unicode-bidi', and 'word-spacing' require some 
explanation, at least as far as this non-psychic is concerned.

Why are color values containing an alpha component not accepted 
while the 'opacity' property is accepted?



5. CSS Syntax


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?



6. Assigning Property Values, Cascading, and Inheritance

"2. The TV-UA SHALL support inheritence as described in CSS2 
([CSS2] Section 6.2)."

Change "inheritence" to "inheritance".


"4. The TV-UA SHALL support author originating style sheets. The TV-
UA MAY support user or user-agent originating style sheets ([CSS2] 
Section 6.4)."

This imbalance of control is a nasty surprise.  What is the rationale for 
divesting users of their stake in the cascade?  If I could rewrite this 
requirement, it would read "The TV-UA SHALL support user-originating 
style sheets. For some TV-UAs, this will necessitate retrieval of user 
style sheets from the Web. The TV-UA SHOULD support author-
originating and user-agent-originating style sheets ([CSS2] Section 
6.4)."


"5. The TV-UA SHALL support all CSS2 cascading rules ([CSS2] 
Sections 6.4.1-6.4.4)."

To disambiguate, change "rules" to "regulations".



"Appendix A. References"

Please give the status of each reference as either normative or non-
normative.

-- 
Etan Wexler <mailto:ewexler@stickdog.com>

Received on Tuesday, 4 June 2002 15:11:52 UTC