The way that I read the definition, tu'a extracts one sumti from within
the first layer of an abstraction. Thus "tu'a ko'a" amounts to something
like "lo su'u ko'a (se'o'e) co'e (kei)" (using xorlo) but not "lo su'u lo
su'u ko'a (se'o'e) co'e kei (se'o'e) co'e (kei)". Thus, I think that it
could be good to have a word for extracting from n (quite probably xo'e)
down.

Comment #2: Re: From how many layers down does tu'a extract?

Jonathan (Tue Aug 4 20:06:57 2015)

I don't think there is a need for that. co'e could mean any predicate, including those that would put the referent into additional abstractions. I'm not sure how it's practical to count the number of layers of abstractions needed, or how that would be any more useful beyond just expanding the abstraction itself.

Comment #3: As many as needed

Wuzzy (Wed Aug 5 11:45:20 2015)

After reading the examples in CLL chapter 11 section 10, it becomes clear to me that "tu'a" can "extract" from as many "layers" of abstraction as needed, not just the first one. https://lojban.github.io/cll/11/10/