ification of the "has" relation seems to be the best way out here.
&gt; &gt; ;; For instance, one could introduce a part-of relation and then explicitly
&gt; &gt; ;; deny that if x is a part of y, then y has x.  But this approach is 
&gt; dubious --
&gt; &gt; ;; how does one distinguish legitimate cases of having -- e.g., a 
&gt; marriage has
&gt; &gt; ;; a husband, a husband a wife -- from illegitimate?
&gt; &gt;
&gt; &gt; (forall (?x)
&gt; &gt;         (=&gt; (instance-of ?x Relative)
&gt; &gt;           