It&#x27;s a guess, but I think GP uses &quot;operational&quot; as a synonym for &quot;imperative&quot;. I think I encountered the term &quot;operational semantics&quot; in the context of Prolog programming. Denotational semantics is a term for a kind of semantics which are mathematically pure. IIRC Prolog has both operational and denotational semantics defined and they conflict. There&#x27;s something about cut operator and tree pruning, but I read this long ago :-)