fore or equal to ?t1.")
&gt; &gt;
&gt; &gt; (forall (?t1 ?t2)
&gt; &gt;         (&lt;=&gt; (beforeEq (?t1 ?t2)
&gt; &gt;                        (and (timepoint ?t1) (timepoint ?t2)
&gt; &gt;                             (or (before ?t1 ?t2) (= ?t1 ?t2))))))
&gt; &gt;
&gt; &gt; (documentation "AXIOM: The exists-at relation holds between physical 
&gt; things and timepoints.")
&gt; &gt;
&gt; &gt; (nth-domain exists-at 1 Physical 2 timepoint)
&gt; &gt;
&gt; &gt; (documentation "AXIOM: The before relation only h