gt; &gt;              (and (Class ?class1)
&gt; &gt;                   (Class ?class2)
&gt; &gt;                   (not (exists (?x)
&gt; &gt;                                (and (instance-of ?x ?class1)
&gt; &gt;                                     (instance-of ?x ?class2)))))))
&gt; &gt;
&gt; &gt; ;;;;;;;;;;;;;;; AXIOMS EXPRESSING THE CLASS HIERARCHY ;;;;;;;;;;;;;;;;;
&gt; &gt;
&gt; &gt; (subclass-of Independent Entity)
&gt; &gt; (subclass-of Relative Entity)
&gt; &gt; (subclass-of Mediating Entity)
&gt; 