I believe parent is referring to the LA-grammar hierarchy[1] of formal languages. 1. https://www.lagrammar.net/monographs/1999/slides/pdf/chapter-11.pdf https:

I believe parent is referring to the LA-grammar hierarchy[1] of formal languages. 1. https://www.lagrammar.net/monographs/1999/slides/pdf/chapter-11.pdf https://www.lagrammar.net/monographs/1999/slides/pdf/chapter... (last slide)