Clarification:
Animations don't map to Elements directly, only via AnimationEffects.
There is a 1:1 mapping between Animations and AnimationEffects.
There is a 1:1 mapping between KeyframeEffects and Elements.
GroupEffects and SequenceEffects have a 1:* mapping to other AnimationEffects.

Once GroupEffect and SequenceEffect are implemented there will be an implicit 1:* mapping between Animations and Elements.

The speccing of GroupEffects is not happening yet, so there isn't much concrete to drive this yet. Alan suggests we should approach this by experimenting with implementing GroupEffects.

This won't be required until Web Animations level 2. Let's wait until that's on our radar before making it an item of work.