About: http://webisa.webdatacommons.org/7722294

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	The syntax is ISNULL(value_to_test,new_value) where the first option is the column or variable to test if there is a NULL value, and the second option will define what to do change the value to if there is a NULL value.
http://www.w3.org/ns/prov#wasQuotedFrom	docstoc.com