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

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<mailto: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<mailto: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...







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