Questions & Discussions (about the course or NLP in general)

indeed:
$X+$ is $X | XX | XXX | XXXX | \cdots$
thus
$(a \otimes b)+$ is $(a \otimes b) | (a \otimes b)(a \otimes b) | (a \otimes b)(a \otimes b)(a \otimes b)| \cdots$
that is
$(a,b) | (aa,bb) | (aaa,bbb) | (aaaa,bbbb) | \cdots$

(since, by concatenation, $(a,b)(a,b)$ is $(aa,bb)$)

Summary:

• $a+\otimes b+ = (a^n, b^m), n\geq1, m\geq1$
• $(a\otimes b)+ = (a^n, b^n), n\geq1$