[ttml2] Remove <animation-value-list> as permissible syntax from <set> definition

palemieux has just created a new issue for https://github.com/w3c/ttml2:

== Remove <animation-value-list> as permissible syntax from <set> definition ==
It looks like the syntax of the animated style property value specified by a `set` element was changed to `<animation-value-list>` at 706f55c1d1f4ddc257eaffa641c475953ca4fc92. This is problematic for the following reasons:

- it expands the syntax in TTML1 without defining a corresponding TTML2 feature
- the expanded syntax is immediately constrained to effectively have the same capabilities as the TTML1 syntax. In other words, processors have to accept a more complex syntax for no benefit
- as discussed at #608, the `<animation-value-list>` currently has fatal problems

Suggest removing the following:

> Style property attributes targeted by an set element are specified directly using attributes in the TT Style namespace or in a namespace that is not some TT Namespace, where the single target animation (key) value adheres to the <animation-value-list> syntax, where each constituent <animation-value> adheres to the syntax of the specified attribute, and where exactly one constituent <animation-value> is specified.
> If more than one constituent <animation-value> is specified, then all constituents other than the first must be ignored for the purpose of presentation processing, and must be considered an error for the purpose of validation processing.


Please view or discuss this issue at https://github.com/w3c/ttml2/issues/633 using your GitHub account

Received on Wednesday, 7 February 2018 18:50:30 UTC