Clarify anonymous span construction and implicit duration semantics #318

palemieux · 2018-01-04T19:28:36Z

Closes #193
Closes #310

cconcolato

Maybe changing "timing semantics" to "timing behavior"?

nigelmegitt · 2018-01-05T13:56:19Z

Build available at https://rawgit.com/w3c/ttml1/issue-193-anon-span-implicit-duration-build/index.html

nigelmegitt

Requesting a formatting change but more importantly I don't agree with the given explanation for the behaviour (I do agree with the described behaviour though!).

nigelmegitt · 2018-01-05T13:58:05Z

spec/ttml1.xml

@@ -8094,6 +8094,30 @@ based timing or event based timing in <bibref ref="smil21"/>, where the specific
 <specref ref="time-expression-semantics-smpte"/> apply.</p>
 </item>
 </ulist>
+<p>The following example illustrates the timing semantics of anonymous spans that are children of sequential time containers. The words <emph>Hello</emph> and <emph>Allo</emph> are both contained in anonymous spans that are children of a sequential time container (the <code>p</code> element). As such, neither <emph>Hello</emph> nor <emph>Allo</emph> will be displayed since the implicit duration of the anonymous spans is 0. In contrast, the word <emph>Bonjour</emph> is contained within an anonymous span that is the child of a parallel time container (the <code>span</code> element). As such, <emph>Bonjour</emph> will be displayed since the implicit duration of the anonymous span is indefinite, resulting in the implicit duration of its <code>span</code>, <code>p</code>, <code>div</code> and <code>body</code> ancestors to also be indefinite. </p>


I think the normal editorial practice is to put the explanation in a Note beneath the example.

I don't think it is true that the word "Bonjour" is contained in an anonymous span. The text in §7.1.5 p:

If a sequence of children of a p element consists solely of character information items, then that sequence must be considered to be an anonymous span for the purpose of applying style properties that apply to span elements.

does not appear in 7.1.6 span so I don't think it applies.

Rather, the reason the word Bonjour appears indefinitely is because the explicit span's implicit duration is indefinite.

Please disregard the previous comment - I've gone and checked and read it again properly and realise that 7.1.6 does have text that provides this behaviour:

The span element accepts as its children zero or more elements in the Metadata.class element group, followed by zero or more elements in the Animation.class element group, followed by zero or more intermixed span elements, br elements, or text nodes interpreted as anonymous spans.

(my emphasis added)

Sorry for the noise.

@nigelmegitt In fact, I think you were right in your first thought. In 9.3.3 it actually says:

for each span element whose child is a single anonymous span, replace the anonymous span with its sequence of child text nodes;

@cconcolato This clause applies when constructing ISDs, which happens after timing is resolved.

@palemieux I'm confused. The creation of 'anonymous spans' is only defined in 9.3.3, therefore for me it does not make sense to talk about timing of an anonymous span, because as you say timing has been resolved already in 9.3.3.

@palemieux TTML2 has a note that covers that:

Note: A compliant presentation processor is permitted to perform the previous step (anonymous span generation) and this step (style resolution) as post-processing steps while performing the [construct intermediate document] procedure, in which case each intermediate synchronic document produced by 11.3.1.3 Intermediate Synchronic Document Construction will contain anonymously generated spans and computed

but I couldn't find this text in TTML1. Maybe this should be backported.

I think we need to understand why that note was added to TTML2.

In fact, TTML2 changed the sentence the span element accepts as its children zero or more elements in the Metadata.class element group, followed by zero or more elements in the Animation.class element group, followed by zero or more intermixed span elements, br elements, or text nodes interpreted as anonymous spans to remove the mention of anonymous spans.

This is a problem since TTML2 also states that If no timeContainer attribute is specified on a span element, then it must be interpreted as having parallel time containment semantics., which leaves the implicit duration of a span undefined if the span element does not contain anonymous spans.

It does seem that we should not have a discrepancy here between TTML1 and TTML2 if at all possible. I've added an agenda item for this, but perhaps it is something that can be covered in offline discussions before the F2F on Tuesday?

Disagreeing with myself

nigelmegitt

The formatting is a little inconsistent but I'm basically happy with the content here.

Clarify procedure for creating anonymous spans (#193) Clarify implicit duration of that contain only text nodes (#193)

palemieux · 2018-01-16T22:38:56Z

Notes on e093565 :

the implicit duration of set elements follows the semantics of anonymous spans
anonymous span construction and pruning has been factored out
the implicit duration of span elements that contain only text nodes follow the semantics of anonymous spans. This means that:

hello behaves the same as hello
anonymous span construction and pruning can take place once for both timing resolution and style resolution

mentions of text nodes being converted to anonymous spans are removed from p and span sections per TTML2
the example in Section 10.4 was updated accordingly

nigelmegitt

One editorial point, one technical issue in the example that certainly needs to be fixed, and one possibly hypothetical or irrelevant question that I'd like to be more certain about before moving forwards with this change.

nigelmegitt · 2018-01-17T22:08:25Z

spec/ttml1.xml

-<p>The implicit duration of a <el>body</el>, <el>div</el>, <el>p</el>,
-or <el>span</el> element is determined in accordance to (1) whether
+<p>The implicit duration of a <el>body</el> element, <el>div</el> element, <el>p</el> element,
+or <el>span</el> element (but not of a <el>span</el> element whose children 


Rather than the parentheses it would be consistent with the previous bullet, and clearer, to say "or span element whose children are not exclusively text nodes".

nigelmegitt · 2018-01-17T22:10:23Z

spec/ttml1.xml

@@ -8106,7 +8123,7 @@ based timing or event based timing in <bibref ref="smil21"/>, where the specific
  &lt;div&gt;
    &lt;p timeContainer=&quot;seq&quot;&gt;
      Hello
-      &lt;span&gt;Bonjour&lt;/span&gt;
+      &lt;p&gt;Bonjour&lt;/p&gt;


This is not valid TTML - a p cannot contain a p.

@nigelmegitt Thanks for the catch!

nigelmegitt · 2018-01-17T22:30:43Z

spec/ttml1.xml

@@ -8094,7 +8110,8 @@ based timing or event based timing in <bibref ref="smil21"/>, where the specific
 <specref ref="time-expression-semantics-smpte"/> apply.</p>
 </item>
 </ulist>
-<p>The following example illustrates the timing semantics of anonymous spans that are children of sequential time containers. The words <emph>Hello</emph> and <emph>Allo</emph> are both contained in anonymous spans that are children of a sequential time container (the <code>p</code> element). As such, neither <emph>Hello</emph> nor <emph>Allo</emph> will be displayed since the implicit duration of the anonymous spans is 0. In contrast, the word <emph>Bonjour</emph> is contained within an anonymous span that is the child of a parallel time container (the <code>span</code> element). As such, <emph>Bonjour</emph> will be displayed since the implicit duration of the anonymous span is indefinite, resulting in the implicit duration of its <code>span</code>, <code>p</code>, <code>div</code> and <code>body</code> ancestors to also be indefinite. </p>
+<p>For the purposes of performing presentation processing, the <phrase role="strong">[construct anonymous spans]</phrase> procedure is applied before resolving begin and end times of content elements.</p>


Is all of [construct anonymous spans] performed before resolving begin and end times? Consider:

 Wibble Wobble Wibble 

Before 2s and after 3s, if you resolve the timing before step 2 of [construct anonymous spans] there are two contiguous anonymous spans that get replaced by a single anonymous span in step 2. Between 2s and 3s the anonymous spans are not contiguous.

If you resolve the timing after completing [construct anonymous spans] then the anonymous spans are never contiguous.

The next question is: does it ever make any difference? I think it makes no difference, but then I wonder what the point of step 2 is at all, and suspect I've missed something... Any further thoughts or ideas @palemieux @skynavga ?

but then I wonder what the point of step 2 is at all, and suspect I've missed something

FWIW, I think of step (2) as a clean-up pass that create a single anonymous span from the multiple text nodes that an XML element can have.

nigelmegitt · 2018-01-18T09:54:10Z

Thanks @palemieux those changes fix the main issues. I'd like to cover #318 (comment) on the call later today, hopefully briefly, before I approve this pull.

nigelmegitt

See also the point discussed today (minutes); following that discussion, I'm approving this.

Add example illustrating anon spans in seq containers (#193)

6fe3786

palemieux added this to the 3rd Ed milestone Jan 4, 2018

palemieux self-assigned this Jan 4, 2018

skynavga mentioned this pull request Jan 4, 2018

Inconsistent implicit duration of singleton span in sequential container. #193

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cconcolato reviewed Jan 4, 2018

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nigelmegitt previously requested changes Jan 5, 2018

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nigelmegitt added the agenda label Jan 5, 2018

palemieux removed the agenda label Jan 10, 2018

Specify <set> implicit duration (#310)

e093565

Clarify procedure for creating anonymous spans (#193) Clarify implicit duration of that contain only text nodes (#193)

palemieux changed the title ~~Add example illustrating anon spans in seq containers~~ Clarify anonymous span construction and implicit duration semantics Jan 16, 2018

palemieux added the agenda label Jan 16, 2018

nigelmegitt requested changes Jan 17, 2018

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Address comments

16ea678

nigelmegitt approved these changes Jan 18, 2018

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Merge branch 'master' into issue-193-anon-span-implicit-duration

f99fb70

palemieux removed the agenda label Jan 21, 2018

palemieux merged commit 62ca221 into master Jan 21, 2018

cconcolato mentioned this pull request Jan 29, 2018

Misuse of span in sentences #335

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skynavga mentioned this pull request Feb 14, 2018

Introduce anonymous span creation procedure (#358). w3c/ttml2#603

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skynavga deleted the issue-193-anon-span-implicit-duration branch March 11, 2018 22:47

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Clarify anonymous span construction and implicit duration semantics #318

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Clarify anonymous span construction and implicit duration semantics #318

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