W3C home > Mailing lists > Public > public-tt@w3.org > April 2014

Re: issue-299, action-254 wording

From: Glenn Adams <glenn@skynav.com>
Date: Sat, 26 Apr 2014 19:05:07 -0600
Message-ID: <CACQ=j+csKXsSLJwXozrCTxsrD7oo3pLGzZEXTGdMwHXNVgASzg@mail.gmail.com>
To: Nigel Megitt <nigel.megitt@bbc.co.uk>
Cc: Timed Text Working Group <public-tt@w3.org>
On Fri, Apr 25, 2014 at 6:36 AM, Nigel Megitt <nigel.megitt@bbc.co.uk>wrote:

>  Hi Glenn,
>  Did you spot in SMIL3 ยง5.4.5 [1] at the end it describes the behaviour
> of 0 duration elements? This suggests to me an inconsistency in SMIL3 that
> may not have been intended.
>  [1] <http://www.w3.org/TR/2008/REC-SMIL3-20081201/smil-timing.html#Timing-TimeContainerDuration>
> http://www.w3.org/TR/2008/REC-SMIL3-20081201/smil-timing.html#Timing-S<http://www.w3.org/TR/2008/REC-SMIL3-20081201/smil-timing.html#Timing-SemanticsOfTimingModel>
> emanticsOfTimingModel<http://www.w3.org/TR/2008/REC-SMIL3-20081201/smil-timing.html#Timing-SemanticsOfTimingModel>

I noted this in my description on our last call, however, the language you
refer to is making reference to the notionally computed value of simple
duration as opposed to the explicit value of the attribute. Clearly, the
semantics of what simple duration of zero means is supported by the text of
SMIL3. What isn't clear is why the language describing the dur attribute
proscribes the explicit use of zero. As far as I know, there is no reason
to rule it out. I mentioned that we may want to check with Dick Bulterman
(one of the main authors of SMIL) to see if he recalled any background on
this point.

>  In your wording for this issue [2] you use the word 'willful' which in
> my understanding has negative connotations, that don't apply here! It would
> be better to replace "willful violation of" with "deliberate divergence
> from" to avoid this. In recognising that we are deliberately diverging from
> SMIL we should also explain why we are doing so, in a Note.

The phrase "willful violation" is the standard term for this notion in
HTML5 [1] and a growing variety of W3C specs. It makes more sense to use
the same phrase than invent a euphemism for an accepted term.

Yes, we could add a note, but it would be something like (or equivalent to):

"We don't understand why SMIL proscribes zero value for the dur attribute,
particularly when it explicitly discusses a simple duration of zero in a
number of other contexts. We did not prohibit a value of zero in TTML1 and
see no reason to prohibit it now."

However, the utility of such a note seems minimal, so I'm uncertain it is
worth adding. Perhaps you can find a better phrasing worth adding in a note?


>  [2]
> https://dvcs.w3.org/hg/ttml/raw-file/default/ttml2/spec/ttml2.html#timing-attribute-dur
>  Kind regards,
>  Nigel
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Received on Sunday, 27 April 2014 01:05:56 UTC

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