prov/commit

use proper predicate to log entity use

diff --git a/lib/prov_schema.pl b/lib/prov_schema.pl
index a36a3de..6c4d111 100644
--- a/lib/prov_schema.pl
+++ b/lib/prov_schema.pl
@@ -237,12 +237,11 @@ log_entity_create(File, Options) :-
     log_entity_graph_properties(Entity, Graph, ProvBundle).
 
 log_derivation(Entity, Options) :-
-    option(activity(Activity), Options),
     option(was_derived_from(Sources), Options),!,
     option(prov(ProvBundle), Options),
     forall(member(Source, Sources),
            (   uri_file_name(SourceUri, Source),
-               rdf_assert(Activity, prov:used, SourceUri, ProvBundle),
+               log_entity_use(SourceUri, Options),
                rdf_assert(Entity, prov:wasDerivedFrom, SourceUri, ProvBundle)
            )
           ).