the code looks fine; we just have to be careful when adding fields to the spec, both when merging forward, and in terms of back porting to libsdformat6 and libsdformat9

do you have a plan for forward and back-porting?

do you have a plan for forward and back-porting?

We currently don't need this in earlier versions but I can backport it if we want to keep the spec consistent?

What's the process for merging forward? Should I create separate PRs to add the field to the 1.8 (sdf11) and 1.9 (sdf12) specs?

do you have a plan for forward and back-porting?

We currently don't need this in earlier versions but I can backport it if we want to keep the spec consistent?

this would be easier if we kept the spec and parser in separate repositories. we'd probably need to add a patch number to the spec to handle new fields (i.e. 1.6.1). Until then, let's try to keep them consistent

What's the process for merging forward? Should I create separate PRs to add the field to the 1.8 (sdf11) and 1.9 (sdf12) specs?

you can copy them over to the new specs in the merge-forward pull request

sounds good, I merge this first and then start porting to other branches.