process, just an individual data entry error.
&gt;
&gt;MW: This case is not dealt with in database design, and so not
&gt;included in data models (actually EXPRESS can do this sort of
&gt;constraint, but this feature is not widely used).
&gt;
&gt; &gt; Note that there
&gt; &gt; may be thousands of such entirely random errors created by
&gt; &gt; tired data entry
&gt; &gt; clerks.
&gt;
&gt;MW: Indeed, but your axiom will only pick up a small percentage
&gt;of them.

That particular axioms, of course, which i