Hi there, When talking about negation, is the following possible in SWRL: Company(?x) ^ Company(?y) ^ buys(?x, ?y) => !hasCompetitor(?x, ?y) In natural language: If ?x and ?y are companies and company ?x buys company ?y, than the property "hasCompetitor" between ?x and ?y has to be removed. -- Best regards, Jethro Borsje http://www.jborsje.nl/