query: #title: Missing subclass link
  # Complex constraint from [[Property talk:P2738]]
  # Disjoint union of classes which are not listed as subclasses of the item
  SELECT distinct ?item ?sub WHERE {
    ?item p:P2738 / pq:P642 ?sub .
    FILTER NOT EXISTS { ?sub wdt:P279 / wdt:P279? / wdt:P279? ?item . }
  }