query: SELECT DISTINCT ?item ?itemLabel ?value1Label
  WHERE 
  {
    {?item wdt:P31 wd:Q43229.} #instance of organisation
    MINUS {?item wdt:P1454 ?value1.} #where legal form is missing
    {?item wdt:P5164 ?value.} #belongs to Flanders Art Institute
    SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
  }