y in this forum!

&gt; &gt; &gt; note: relations between classes (e.g. subclass-of) are only
&gt; &gt; &gt; allowed when the nature of the constraint they define is defined
&gt; &gt; &gt; by a lambda expression.
&gt; &gt;
&gt; &gt; Relations don't define anything; they are just (for you) sets of
&gt; &gt; ordered pairs.  And it is looking more and more like a constraint is
&gt; &gt; just a condition like the one above.  I think you should leave
&gt; &gt; "lambda" out of it!
&gt;
&gt; MW: fine, (its all Gree