Using log:outputString (example)

@prefix names: <foo:> .
@prefix log: <http://www.w3.org/2000/10/swap/log#> .
@prefix string: <http://www.w3.org/2000/10/swap/string#>.

{  ?x names:familyName ?k.
   (?x.names:givenName " " ?x.names:familyName " has been invited\n" )
         string:concatenation  ?s.
} => {
   ?k  log:outputString ?s.
}.

[ names:familyName "Hawke"; names:givenName "Sandro" ].
[ names:familyName "Connolly"; names:givenName "Dan" ].
[ names:familyName "Berners-Lee"; names:givenName "Tim" ].

cwm example.n3 --think --strings

Tim Berners-Lee has been invited
Dan Connolly has been invited
Sandro Hawke has been invited