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RE: Media TextFormats Accessibility Comparison Summary Released

From: Sean Hayes <Sean.Hayes@microsoft.com>
Date: Thu, 6 Jan 2011 10:31:30 +0000
To: Silvia Pfeiffer <silviapfeiffer1@gmail.com>, HTML Accessibility Task Force <public-html-a11y@w3.org>
CC: Henri Sivonen <hsivonen@iki.fi>
Message-ID: <8DEFC0D8B72E054E97DC307774FE4B91331204CB@DB3EX14MBXC313.europe.corp.microsoft.com>
This is not a valid observation. As has been explained previously on the list. There is no requirement to use an XSL-FO formatter to process TTML. XSL-FO is used as an expositional tool by the specification for the purposes of describing intended effect. There have been at least 2 implementations of TTML written using CSS as the formatting engine.

<quote href="http://www.w3.org/TR/ttaf1-dfxp#styling">
Styling attributes are included in TTML to enable authorial intent of presentation to be included within a self-contained document. This section describes the semantics of style presentation in terms of a standard processing model. TTML Processors are not required to present TTML documents in any particular way; but an implementation of this model by a TTML Presentation Processor that provides externally observable results that are consistent with this model is likely to lead to a user experience that closely resembles the experience intended by the documents' authors. 

The semantics of TTML style presentation are described in terms of the model in [XSL 1.1]. The intended effect of the attributes in this section are to be compatible with the layout model of XSL. Presentation agents may however use any technology to satisfy the authorial intent of the document. In particular since [CSS2] is a subset of this model, a CSS processor may be used for the features that the models have in common.

-----Original Message-----
From: public-html-a11y-request@w3.org [mailto:public-html-a11y-request@w3.org] On Behalf Of Silvia Pfeiffer
Sent: 06 January 2011 09:26
To: HTML Accessibility Task Force
Cc: Henri Sivonen
Subject: Re: Media TextFormats Accessibility Comparison Summary Released

Dear media a11y members of the a11y TF,

I think Henry has made a valid observation and we should clarify the boxes that talk about xml.

Here's what I suggest changing on the wiki page:

For TTML change the box that contains:
"The XML root of TTML is seen as a problem by some implementers and authors."
"The XML root of TTML is seen as a problem by some implementers and authors. In particular the use of the XSL-FO formatting model which is not already implemented by browser engines poses a major issue."

For WebSRT/WebVTT change the box that contains:
""Is not XML.""
""Is not XML." In particular it reuses the CSS formatting model rather than XML-based formatting models."


On Thu, Jan 6, 2011 at 10:18 AM, Silvia Pfeiffer <silviapfeiffer1@gmail.com> wrote:
> You are right - XSL-FO has not been explicitly spelled out as a 
> problem with TTML. Instead, it has been subsumed under "The XML root 
> of TTML is seen as a problem by some implementers and authors.".
> It is probably worth adding these objections explicitly rather than 
> staying vague about them.
> Regards,
> Silvia.
> On Mon, Jan 3, 2011 at 4:20 PM, Henri Sivonen <hsivonen@iki.fi> wrote:
>> On Dec 17, 2010, at 20:15, Janina Sajka wrote:
>>> The comparison summary document is available at:
>>> http://www.w3.org/WAI/PF/HTML/wiki/TextFormat_Comparison_Overview
>> I obverse that the comparison fails to mention the use of a formatting model (XSL-FO) that isn't already implemented by browser engines as an "issue" for TTML (and fails to mention the use of the CSS formatting model as a strength of WebSRT/WebVTT). This is a rather central omission in the comparison.
>> --
>> Henri Sivonen
>> hsivonen@iki.fi
>> http://hsivonen.iki.fi/
Received on Thursday, 6 January 2011 10:42:25 UTC

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