; (documentation Occurrent  "An entity that does not have a stable identity
&gt; &gt;  during any interval of time.  Formally, Occurrent is a primitive that
&gt; &gt;  satisfies the following axioms: \
&gt; &gt;    * The temporal parts of an occurrent, which are called stages,
&gt; &gt;      exist at different times. \
&gt; &gt;    * The spatial parts of an occurrent, which are called participants,
&gt; &gt;      may exist at the same time, but an occurrent may have different
&gt; &gt;      participants at 