Should the representation of tactile graphics be specified here or elsewhere?

This specification refers to the inclusion of tactile graphics and allows for various graphics formats to be included in eBraille publications, but it doesn't prescribe how tactile graphics should be represented.

For instance, which file formats are preferred? Is a vector-based representation preferable to enable better scaling? How should braille labels be represented in supported image formats?

I think this specification should at least indicate where and how such issues are to be addressed, even if they're out of scope here.