<http://webisa.webdatacommons.org/prov/435539747>	<http://www.w3.org/ns/prov#wasDerivedFrom>	<http://webisa.webdatacommons.org/321618866> .
<http://webisa.webdatacommons.org/321618866>	<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>	<http://www.w3.org/ns/prov#Entity> .
<http://webisa.webdatacommons.org/321618866>	<http://www.w3.org/ns/prov#wasQuotedFrom>	<fiid.net> .
<http://webisa.webdatacommons.org/321618866>	<http://www.w3.org/ns/prov#value>	"Deleting a message is a good example: for a spool file ??? the message must be removed, and then the whole file after the deleted message must be rewritten with the deleted message removed, which is a very expensive operation." .