Transforms must describe how to animate by- to- animations. Paced animations can be unspecified for now with a note that future specs will define it.
Resolution of SVG WG.
This bug also includes a definition for additive and accumulative transformations.
Resolution SVG WG.
I think the definitions should be independent of SVG since "Web animations" might rely on it in the future.
After reviewing the SVG animation section again, I come to the conclusion that the spec text is good enough and needs implementation feedback.
Closing this bug.