an Entity references as follows:
Revision is a derivation (see http://www.w3.org/TR/prov-dm/#term-Revision). Moreover, according to http://www.w3.org/TR/2013/REC-prov-constraints-20130430/#term-Revision 23 April 2012 'wasRevisionOf is a strict sub-relation of wasDerivedFrom since two entities e2 and e1 may satisfy wasDerivedFrom(e2,e1) without being a variant of each other.'