
entity, relation and expression classifications are regarded as
interpretation functions.<br>
</p>
<div style="text-align: justify;">An IFF <span
 style="font-style: italic;">model </span>(model-theoretic
structure) extends a type language to a universe of discourse
(containing entities) and a tuple space. Both entities and tuples are
untyped <a href="http://www.utm.edu/research/iep/a/apriori.htm">a
priori</a>. An IFF model types and interprets the entities and
tuples via classifications &#8211; there is a