be about/? to do something: ADJ, ADV, or ADP?

[nschneid]

https://universal.grew.fr/?custom=650f89d98e82c

[nschneid]

Remarks:

• GUM has exclusively ADV. EWT has a mix of ADV and ADJ.
• Neither corpus has about/ADJ outside of this construction. This makes me suspicious of ADJ, along with the fact that the infinitival is mandatory: We are ready (to leave) but *We are about. (Though I suppose likely and inclined are ADJs that can predicate with an infinitival but resist taking agentive subjects without the infinitival, aside from the idiom be so inclined.)
• Dictionaries I checked are mixed. MW and OED say Adv. Collins COBUILD, Longman, and Oxford Advanced Learner's say Adj. @brettrey also has Adj, which may be influenced by CGEL's narrow view of the Adv category (CGEL AdvPs can't be complements of be).
• WordNet doesn't have this usage but does have a related usage under Adv: The job is about done. The only Adj sense it has is "up and about".
• OntoNotes 5 prefers Adj but is mixed: 43 JJ tokens, 20 IN, 4 RB

There's also the question of the correct structure:

• (A) "about" as head of predicate with xcomp dependent, or
• (B) "about" as advmod of following predicate (perhaps fixed à la "so as to")

[nschneid]

I suppose the treatment of semi-auxiliaries like "ought to" and "have to" is relevant (#411). For the sake of argument:

• (C) "about" as AUX/aux of following predicate, and "be" as the progressive auxiliary rather than the copula
  • "ought to" uses the xcomp analysis though, despite "ought" being tagged AUX, so that weighs against the shallow structure
• (D) "about" as AUX with xcomp dependent, like "ought"
• (E) "about" as ADP attaching as mark alongside "to" (also mark)

[nschneid]

An argument against (B) is that the position of an advmod in a clause is often flexible, but this is not the case with "about to":

• Soon, he will leave. He will soon leave. He will leave soon.
• About, he is to leave. About to, he is leave. He is about to leave. He is to leave about. He is leave about to.

"so as to" differs because it attaches as mark, which is expected to occur at the beginning of the clause.

[nschneid]

Argument against AUX: "about to" can appear in a predicative adjunct, e.g. "(Being) about to leave, the president was stopped by an aide". This suggests that when "be" is present, either in an adjunct or in a main clause, it is the copula, not the progressive aux. The copula would not normally be followed by an aux.

So I am leaning toward (A) for the structure and ADJ or ADV for the tag.

[amir-zeldes]

Would definitely vote for xcomp dependent. For POS I would try to follow ON, so I would prefer JJ/ADJ, and can fix GUM.