"Mary Lee Pfeiffer (A) is Tom Cruise's (B's) mother" and "Tom Cruise (B) is Mary Lee Pfeiffer's (A's) son" are two statements of the same relation.
EDIT: I mean if you'd go so far, even Tom Cruise could have multiple mothers, but that doesn't make "Mary Lee Pfeiffer is Tom Cruise's mother" a wrong statement, just because "one of ... mothers" is missing.
Might have several. It only has one answer if there is only one child, which appears to be the case here. They are measuring against what they told the model, not necessarily facts mapping to the real world.
In this case, the correct would always include “Tom Cruise” even if it needed a clarifying “there might be others I have no knowledge of”.
With context. It does have several which was probably GPs point, and she did not have only one child.
Quick google search turns out that Mary Lee Pfeiffer had 4 children:
Lee Ann DeVette (born 1959) (daughter) Marian Henry (born 1960) (daughter) Tom Cruise (born 1962) (son) Cass Mapother (born 1964) (daughter)
So saying "Who is Mary Lee Pfeiffer's child?" would have 4 possible answers (which is several) with all known context. Whereas like GP was saying "Who is Mary Lee Pfeiffer's son?" would have 1 identifying answer, Tom Cruise with the same context.
> In this case, the correct would always include “Tom Cruise” even if it needed a clarifying “there might be others I have no knowledge of”.
I agree with this by the way.
My understanding is she has four.
Isn't the right way to phrase that question be "Who are Mary Lee Pfeiffer's children?" to get multiple answers?
Kind of a weird way to draw an analogy, but in math it's kind of like |x|=2 (the absolute value of x is 2) the answer for the value of x is -2 and 2 sure you could reply that the answer is 2 and be correct (even though you would still be missing something, because the space of possible answers includes both 2 and -2). To relay that back to Mary Lee Pfeiffer saying she has Tom Cruise as a child is correct, but the actual answer could include any 4 of her children (including Tom or one of the 3 daughters) and still be correct.
The question "Who is her child" has multiple answers because it asks you to deliver a single answer.
The difference is how you speak about a group term, not the meaning of the word 'to be'.
