What research problem is addressed in the paper titled "6th Open Challenge on Question Answering over Linked Data (QALD-6)"?

SELECT DISTINCT ?concept ?rlabel 
WHERE {
  orkgr:R6386 orkgp:P31 ?x .
  ?x orkgp:P32 ?concept.
  ?concept rdfs:label ?rlabel.
}
LIMIT 1