 that in a given universe A there are many different
| permissible interpretations of the symbols of $L$.  Suppose
| that $A$ = &lt;A, $I$&gt; and $A$’ = &lt;A’, $I$’&gt; are models for $L$
| and that R and R’ are relations of $A$ and $A$’, respectively.
| We say that R’ is the 'corresponding relation' to R if they are
| the interpretations of the same relation symbol in $L$, that is:
|
|    $I$(P) = R  and  $I$’(P) = R’  for some P in $L$.
|
| We introduce similar conventions as regards the