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Re: W3C-transformation language petition


Subject: Re: W3C-transformation language petition
From: Ian Hickson <py8ieh@xxxxxxxxxx>
Date: Wed, 10 Mar 1999 16:24:46 +0000 (BST)

On Thu, 4 Mar 1999, Chris Maden wrote:
>> Will XSL be able to cope with alternative (non graphic) media? CSS
>> can. This is quite an important issue.
> Short answer: XSL must because of the W3C's commitment to the WAI.
> It's a procedural requirement.
Good.


> But consider the ability to structure the formatted document,
> providing HTML-<object>-like sets of alternatives, or audio and
> visual formatting objects with specified relationships to each
> other.

Hmm.

FOs (in their current form) are rather firmly linked to visual media
(page, screen, projection), just like in CSS the 'color', 'border',
'font', etc..., properties are firmly linked to the visual media.

To get comprehensive styling for multiple media (aural, visual,
tactile) would require multiple sets of FOs.

For example, in visual media a comment may be rendered as a sidebar,
while in aural media it may be rendered as a little audio cue which
links to the actual comment at the end of the audio stream.

This cannot be done easily using a single set of FOs (indeed, that is
one of the problems with CSS: there is no transformation step).

The only possible solutions I see are:

 a. Have one XSL stylesheet for each media type.
 b. Have an @media equivalent (this is mentioned in the current
    draft).

In either case, the document needs a separate transformation step for
each media type. I have serious doubts that authors will generally
write an XSL stylesheet for more than one media. This is a problem.


>> Quite seriously, what is it that in the opinion of FO proponents is
>> missing from CSS? (Other than tree transformation, obviously.)
> Structured output is a big thing.

Yes, but that is tree transformation. I am talking only about the FO
part now. 

I fully admit that CSS, to be effective, needs a transformation
language to go with it. XSL-transformation can be this language.


> XML syntax is ideal for representing crosslinked trees, and a
> formatted document is full of such relationships (page number
> dependencies, allocating sidebar space on the screen, "above" or
> "below" conditional text). 

Absolutely. But this kind of thing is out of the scope of CSS, and is
not what FOs are (AFAICT) going to be used for.


-- 
Ian Hickson 
U+2642 U+2651
U+262E U+2603 U+263A


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