About: http://webisa.webdatacommons.org/383914054

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	Thus to test if a column is NULL or is not NULL, a special syntax must be used: either 'column IS NULL' or 'column IS NOT NULL'.
http://www.w3.org/ns/prov#wasQuotedFrom	oracle.com