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Re: questions on TTML specification

From: Glenn Adams <glenn@skynav.com>
Date: Mon, 30 Jul 2012 10:25:55 -0600
Message-ID: <CACQ=j+d8Pd-js7RwdwdBoAjefwDE4XjgMfsnHuFX4r1Ka8xd3w@mail.gmail.com>
To: Kouichi Uchimura <Kouichi.Uchimura@jp.sony.com>
Cc: public-tt@w3.org
uchimura-san, thanks for the good questions, which i attempt to answer
inline below

regards, glenn

On Sun, Jul 29, 2012 at 6:41 PM, Kouichi Uchimura <
Kouichi.Uchimura@jp.sony.com> wrote:

> Hi,
> I have some questions to TTML specificaton.
> I appriciate if you reply my questions.
> Forgive me if there were same questions in archive...
> (a) What is expected if tts:backgroundColor is applied to body element?

according to step (6) of [1], body is logically mapped to an outer fo:block
element, which, in turn, would have as its children the fo:block elements
mapped from tt:div; therefore, if tts:backgroundColor is specified on
tt:body, it would apply to that outer fo:block;

keep in mind that an implementation doesn't have to use XSL-FO directly;
rather, the TTML spec uses XSL-FO as only a specification mechanism to
define formatting semantics

[1] http://www.w3.org/TR/ttaf1-dfxp/#semantics-region-layout-step-2

> (b) What is correct understanding of PRUNE (E) (defined in 9.3.2)
>   ==>
>     prune the element and its descendant elements
>   or
>     prune the element and set its parent element as parent element of
>      its child elements

the first: "prune the element and its descendant elements"; note well that
the traversal order for pruning is postorder (see step 2 of the first set
of rules in 9.3.2 [2]), and not preorder, which means that children are
processed (and possibly pruned) before their parent

[2] http://www.w3.org/TR/ttaf1-dfxp/#semantics-region-layout-step-1

> (c) region reference
>   what is expected in following example?
>   <definitions of regions>
>    <body>
>      <div>
>        <p>
>          oh
>          <span region="r1">
>             my
>          <span region="r2">
>             god
>           </span>
>           </span>
>        </p>
>       </div>
>     </body>
>  ==> which region(s) "oh" will be appeared?
>     both r1 and r2? or will "oh" not be appeared?

assuming for a moment that both regions r1 and r2 and the above content
elements are temporally active over the interval of interest, then "oh"
will appear in both r1 and r2; however, "god" appears in neither region due
to the parent span being pruned under r2;

constructing the intermediate document using the first set of rules in
9.3.2 [2] we have:

<region xml:id="r1">
        <!-- <span region="r2"> god </span> pruned -->
<region xml:id="r2">
        <!-- <span region="r1"> my <span region="r2"> god </span> </span>
pruned -->

keep in mind that 9.3.2 step 2 says "postorder" traversal, and not
"preorder", which means that children will be pruned prior to their parent;
also, keep in mind that step 4 refers to the "original" body element, and
not the replicated body elements reparented to region elements in step 3

> (d) region style prop inheritance
>   what is expected in following example?
>     <definition of r1 and r2 (no tts:color definitions in both)...>
>     <body>
>      <div region="r1" tts:color="red">
>        <p begin="1s" end="2s">
>          text1
>        </p>
>        <p region="r2" begin="1s" end="2s">
>          text2
>       </div>
>     </body>
>   ==> what is the color of "text2"?

according to [3], style inheritance operates on the intermediate synchronic

For the purpose of determining inherited styles, the element hierarchy of
an intermediate synchronic document form of a TTML document instance must
be used, where such intermediate forms are defined by *9.3.2 Intermediate
Synchronic Document


The intermediate synchronic document form is utilized rather than the
original form in order to facilitate region inheritance processing.
[3] http://www.w3.org/TR/ttaf1-dfxp/#semantics-style-inheritance

however, due to the intermediate document construction rules described
above, "text2" will never appear since it will be pruned from region r1
(since it is explicitly associated with r2) and will be pruned from region
r2 (since its ancestor div is explicitly associated with r1);
Received on Monday, 30 July 2012 16:26:51 UTC

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