out-of-line-animation

The current TTML2 ed draft [1] definition of [out-of-line-animation] in §2.2:

[out-of-line animation]

An animate<https://dvcs.w3.org/hg/ttml/raw-file/default/ttml2/spec/ttml2.html#animation-vocabulary-animate> or set<https://dvcs.w3.org/hg/ttml/raw-file/default/ttml2/spec/ttml2.html#animation-vocabulary-set> element that is defined out-of-line from the content element<https://dvcs.w3.org/hg/ttml/raw-file/default/ttml2/spec/ttml2.html#terms-content-element> or region<https://dvcs.w3.org/hg/ttml/raw-file/default/ttml2/spec/ttml2.html#layout-vocabulary-region> element targetted by the animation. An out-of-line animation appears as a child of an animation<https://dvcs.w3.org/hg/ttml/raw-file/default/ttml2/spec/ttml2.html#animation-vocabulary-animation> element in the header (head<https://dvcs.w3.org/hg/ttml/raw-file/default/ttml2/spec/ttml2.html#document-structure-vocabulary-head> element) of a document instance<https://dvcs.w3.org/hg/ttml/raw-file/default/ttml2/spec/ttml2.html#terms-document-instance>, and specifies an xlink:href attribute that associates it with the element to be animated. There is a one-to-one relation between an out-of-line animation element and a content element<https://dvcs.w3.org/hg/ttml/raw-file/default/ttml2/spec/ttml2.html#terms-content-element> or region<https://dvcs.w3.org/hg/ttml/raw-file/default/ttml2/spec/ttml2.html#layout-vocabulary-region> element.

specifies a one-to-one relation, as does the mechanism, using a single xlink:href attribute in the animate and set elements; however I thought one of the use cases that had been mentioned in the past (ref?) was to allow a single animation specification to be used by multiple content elements and thereby avoid unnecessary duplication across the document.

I wonder if we need a richer content selection mechanism than xlink:href in this instance: 2 approaches come to mind:

1. Analogous to the way styling is applied, allowing content to reference animations rather than the other way around, or
2. allowing a more generic mechanism that can return multiple nodes such as an xpath 2 path selector, as an alternative to an href.

I'd welcome any thoughts from those hoping to use animation features in TTML2 on this.

Kind regards,

Nigel


This comment relates to the implementation for the following issues in the tracker: issue-22 issue-227 issue-23 issue-72 as included in change proposal 8 [2] and the response should be considered in the context of change proposal 16 [3] for applying conditional styling.

[1] https://dvcs.w3.org/hg/ttml/raw-file/default/ttml2/spec/ttml2.html
[2] https://www.w3.org/wiki/TTML/changeProposal008
[3] https://www.w3.org/wiki/TTML/changeProposal016