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Re: ISSUE-303 (<a> link element): Permit HTML-style <a> elements to contain href links [TTML2]

From: Glenn Adams <glenn@skynav.com>
Date: Tue, 25 Mar 2014 11:15:42 -0600
Message-ID: <CACQ=j+dA=EMWojo_jjgmimsUg5wUsVvEHd_oB921i6xfGCNssg@mail.gmail.com>
To: Nigel Megitt <nigel.megitt@bbc.co.uk>
Cc: Andreas Tai <tai@irt.de>, Timed Text Working Group <public-tt@w3.org>
On Tue, Mar 25, 2014 at 10:34 AM, Nigel Megitt <nigel.megitt@bbc.co.uk>wrote:

>  On 25/03/2014 16:20, "Glenn Adams" <glenn@skynav.com> wrote:
>
>   Compatibility with HTML, longer typing with xlink format, lack of
> implementation of xlink, active removal of support for xlink syntax from
> some SVG UAs, etc.
>
>
>  Thanks.
>
>
>  I would also prefer to ditch xml:id in favor of straight 'id', or
> perhaps restore 'id' as an alternative.
>
>
>  That needs to be raised as a separate issue.
>

Already did [1], but withdrew the proposal recently. It could always be
resurrected.

[1] http://www.w3.org/AudioVideo/TT/tracker/issues/205


>
>
>
> On Tue, Mar 25, 2014 at 10:12 AM, Nigel Megitt <nigel.megitt@bbc.co.uk>wrote:
>
>>  Any pointers to technical reasons why unqualified href is preferred and
>> xlink not?
>>
>>
>>   On 25/03/2014 16:04, "Glenn Adams" <glenn@skynav.com> wrote:
>>
>>   FYI, the SVG WG is backing away from Xlink syntax, reverting to older
>> unqualified @href. I would be reluctant to introduce Xlink features.
>>
>>
>> On Tue, Mar 25, 2014 at 5:21 AM, Nigel Megitt <nigel.megitt@bbc.co.uk>wrote:
>>
>>>  Thanks for the suggestion Andreas. It looks as though the only change
>>> needed to my proposal is to put the href and target attributes into the
>>> xlink namespace in order to create xlink 'simple' links. This is very
>>> similar to the approach taken by SVG with the <a> element [2], which seems
>>> to be an appropriately close example to take inspiration from.
>>>
>>>  [2] http://www.w3.org/TR/SVG11/linking.html#Links
>>>
>>>  To complete the definition we could also consider adding in the xlink
>>> behaviour attributes show and actuate.
>>>
>>>  This could be very helpful for extending TTML to permit referencing of
>>> external image resources in place of text, for example, by setting
>>> show="embed" actuate="onLoad". Note that the temporal extent of the
>>> rendering of such an external resource would be identical to that defined
>>> in TTML depending on the location of the <a> element, which does not itself
>>> have begin and end attributes. This could be extended to audio clips noting
>>> that the playback temporal extent would be clipped by the applicable
>>> temporal extent, in the case that the audio clip has a longer temporal
>>> extent than the applicable TTML temporal extent.
>>>
>>>  Links that the user may follow, to be loaded in a different context,
>>> i.e. not replacing the TTML content, would have show="new" or show="other"
>>> and actuate="onRequest". I would leave it up to implementations to define
>>> how the request mechanism may work in terms of user interface, but add a
>>> note that if more than one 'onRequest' link is simultaneously displayed
>>> that may add unhelpful complexity due to the need to do more than simply
>>> trigger a 'follow link' action in a time-constrained display, for example
>>> requiring an interaction to decide which link to follow.
>>>
>>>  Links that are automatically followed but loaded in a different
>>> context would have show="new" or show="other" and actuate="onLoad".
>>>
>>>  NB I don't propose to add a mechanism for linking *into* a TTML2
>>> document.
>>>
>>>  Kind regards,
>>>
>>>  Nigel
>>>
>>>
>>>   On 24/03/2014 16:31, "Andreas Tai" <tai@irt.de> wrote:
>>>
>>>   Because TTML is an XML Format you may consider XLink [1] for this
>>> purpose.
>>>
>>> Best regards,
>>>
>>> Andreas
>>>
>>> [1] http://www.w3.org/TR/xlink11/
>>>
>>> Am 21.03.2014 16:23, schrieb Glenn Adams:
>>>
>>> We had a rule for TTML1: no references to external resources. We will
>>> remove that rule for TTML2 for images and fonts, and perhaps now
>>> anchor/links as well.
>>>
>>>
>>> On Fri, Mar 21, 2014 at 8:24 AM, Timed Text Working Group Issue Tracker
>>> <sysbot+tracker@w3.org> wrote:
>>>
>>>> ISSUE-303 (<a> link element): Permit HTML-style <a> elements to contain
>>>> href links [TTML2]
>>>>
>>>> http://www.w3.org/AudioVideo/TT/tracker/issues/303
>>>>
>>>> Raised by: Nigel Megitt
>>>> On product: TTML2
>>>>
>>>> Permit <a> elements with href and target attributes only, around
>>>> content elements or text.
>>>>
>>>> This appears to be the minimal useful set of attributes around a link
>>>> that may appear in a timed context.
>>>>
>>>> The purpose of the target is to permit the linked content to be loaded
>>>> into an alternate context: one possible use case for this is to allow the
>>>> linked content to be loaded into a different window or iframe without
>>>> interrupting the flow of captions displayed against a video that's being
>>>> watched.
>>>>
>>>> More concretely, this could be used for example for 'go here for more
>>>> information' links or 'go here to vote for candidate X' links. A third
>>>> example could be 'go here for these subtitles in language [xyz]'.
>>>>
>>>> I don't know if this has been raised before, but it seems so obvious
>>>> that I'm surprised I couldn't find an issue for it - happy to be told where
>>>> to look for it if this is a duplicate. Apologies if I'm opening a can of
>>>> worms that everybody would rather stay closed...
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> ------------------------------------------------
>>> Andreas Tai
>>> Production Systems Television IRT - Institut fuer Rundfunktechnik GmbH
>>> R&D Institute of ARD, ZDF, DRadio, ORF and SRG/SSR
>>> Floriansmuehlstrasse 60, D-80939 Munich, Germany
>>>
>>> Phone: +49 89 32399-389 | Fax: +49 89 32399-200
>>> http: www.irt.de | Email: tai@irt.de
>>> ------------------------------------------------
>>>
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>>> Munich Commercial, RegNo. B 5191
>>> Dr. Klaus Illgner-Fehns
>>> ------------------------------------------------
>>>
>>>
>>>
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Received on Tuesday, 25 March 2014 17:16:32 UTC

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