From b03e530eff6216843aaf05c69c766de32d242602 Mon Sep 17 00:00:00 2001
From: "Peter F. Patel-Schneider" Simple Interpretations
is a set of pairs which identify the arguments for which the property is true,
that is, a binary relational extension.
The distinction between IR and IL will become significant below when the semantics of datatypes are defined. +
The distinction between IS and IL will become significant below when the semantics of datatypes are defined. IL is allowed to be partial because some literals may fail to have a referent.
It is conventional to map a relation name to a relational extension directly.