User blog comment:Koteitan/Purely mathematical definition of BMS/@comment-24923514-20191106231524/@comment-24923514-20191107221930

Luckily this definition seems to have a lot in common with the description of BM1 from the article, that helps. I think it's starting to come together for me. However, I have two questions about BM4 and a question about the actual article.

Does (P_y)^a(x) mean "the a-th ancestor of the entry at S_x,y"?

If so, wouldn't that mean some entries might not have any ancestors? For example, if S = (0,1)(1,1)(2,1)(5,0)(4,1), then does S_3,1 not have a parent? And S_1,1 as well?

Finally, would it be ok if I went through the BMS article to fix any grammar mistakes and clarify a few things? I just wanted to check.