PREFIX  dc:  <http://purl.org/dc/elements/1.1/>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> 
PREFIX  :  <http://example.org/>
SELECT  ?book ?discount
 WHERE {
   	?book a :Book ;
   		  :discount ?discount .
   	FILTER(?discount NOT IN ())
}
