I've updated my lessons: Chapter "Negation, Yes/No Questions" Yes/No questions are now defined not only with VERB ala VERB, but generally with PREDICATE ala PREDICATE.https://htmlpreview.github.io/?https:// ... 0000000000
Quote:An Predicate Noun as Subject of the Question
We had already learned the difference between verb and predicate. In Toki Pona are sentences without verb possible. Then nouns serve as predicate nouns or adjectives as predicate adjectives.
In the lessons of B. J. Knight (2003) and the official Toki Pona book of Sonja Lang  yes/no questions with ala are defined only with verbs. But this contradicts their own examples as well as common practice. For example one cannot formulate the question 'Is she a mother? In these lessons I will therefore not adhere to this limitation.
If the yes/no question refers to a predicate noun, the adjective ala is added to it and the predicate noun is repeated.
ona li ' mama ala ' mama ? Is she a parent?
ni li ' jan ala ' jan? Is this a person?
ni li ' kili ala ' kili? Is this a banana?
ni li ' tomo pi telo nasa ala ' tomo pi telo nasa? Is this a pub?
ona li ' jan pi pona lukin ala ' jan pi pona lukin? Is she an attractive person?An Predicate Adjective as Subject of the Question
If the yes/no question refers to a predicate adjective, the adjective ala is added to it and the predicate adjective is repeated.
sina ' pona ala ' pona? Are you OK?
mi ' pona ala ' pona, tawa sina? Do you like me?
suno li ' suli ala ' suli? Is the sun big?
len sina li ' telo ala ' telo? Are your clothes wet?