fy the axioms of the theory. A prologic is sound when every
instance of the universe is normal and every tuple is normal. By
definition, an IFF <span style="font-style: italic;">logic </span>is
a sound prologic. For any prologic, the
sound part of the prologic is obtained by restriction &#8211; the restriction
construction throws away all abnormal instances and restricts the
entity and relation classifications to normal instances. The
restriction passage from prologics to logics and the inclusion of
logics 