The BFO 2020 "bfo-2020-terms.xlsx" Excel workbook "exists at" entry states this relation's domain & range values as "entity" and "temporal region", respectively. The BFO 2020 OWL model does not assert these values on that relation, and I assume this was an oversight. Here are the Excel workbook examples presented for this relation.
"First World War exists at 1914-1916, Mexico exists at January 1, 2000."
Given this statement,
"Mary's left arm" is a '"continuant_part_of_at_some_time" "Mary's body" from Jun 03, 1980 (her birth date) to Nov 18, 2005 (when she unfortunately lost her left arm during a car accident)
, unless there is another OWL-specific implementable solution to include temporality in this binaryized relation, then I do not see how BFO 2020 OWL's "continuant_part_of_at_some_time" relation alone suffices. I think these facts collectively are necessary to assert this statement in OWL. (Note: For the sake of simplicity, I used the BFO universals and not some domain-specific universals.)
"Duration of time that Mary's left arm is a part of Mary's body" instance_of (i.e., rdf:type in OWL) "Temporal Region"
"Mary's left arm" instance_of (i.e., rdf:type in OWL) "Object"
"Mary's body" instance_of (i.e., rdf:type in OWL) "Object Aggregate"
"Mary's left arm" "continuant_part_of_at_some_time" "Mary's body"
"Mary's left arm" exists_at "Duration of time that Mary's left arm is a part of Mary's body"
"Mary's body" exists_at ""Duration of time that Mary's left arm is a part of Mary's body"
The last two facts assert that the arm & body both exist at the same fiat temporal slice of time, which satisfies the temporal portion of the "continuant_part_of_at_some_time" elucidation.