In section A.1.2 (extra grammatical constraints), the part on occurrence operators [1] introduces the term "Kleene operators".

While it may be considered common knowledge what a Kleene operator is (and certainly it can be deducted here from the context), it is the only usage of his name, so I suggest either to drop it, or to reference it, or to change it to say:

"As written, the grammar in A XPath 3.1 Grammar is ambiguous for some forms using the '+' and '*' occurrence indicators, sometimes also referred to as Kleene operators. [...]"


[1] https://www.w3.org/XML/Group/qtspecs/specifications/xquery-31/html/xpath-31-diff.html#parse-note-occurrence-indicators