Re: issue-299, action-254 wording

On 27/04/2014 02:05, "Glenn Adams" <glenn@skynav.com<mailto:glenn@skynav.com>> wrote:




On Fri, Apr 25, 2014 at 6:36 AM, Nigel Megitt <nigel.megitt@bbc.co.uk<mailto:nigel.megitt@bbc.co.uk>> wrote:

Hi Glenn,

Did you spot in SMIL3 §5.4.5 [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.

Good idea – will you contact him?

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.

There's no euphemism involved here – it's simply an unintentional misuse of the word, probably inherited from a rather specific US legal usage [3]. If those who decided to adopt it in HTML5 were aware of the alternative meaning presumably they willfully violated the term! In the spirit of international harmony my proposal still stands.


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?

Let's wait for a response from Dick Bulterman. I suspect the answer may be that "In our limited adoption of SMIL no problems arise from the use of a zero value dur attribute and we therefore permit it, with no specific use case in mind."


[1] http://www.w3.org/TR/2014/CR-html5-20140204/introduction.html#willful-violation



[2] https://dvcs.w3.org/hg/ttml/raw-file/default/ttml2/spec/ttml2.html#timing-attribute-dur


[3] http://en.wikipedia.org/wiki/Willful_violation


Kind regards,

Nigel




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