riate values.


<p><hr>
<h2><a id="filcl">Filter Clauses</a></h2>

<p>The generator clauses produce - independent from each other - lots of
objects, which match the patterns of individual generator clauses, but not
necessarily the desired result set of the total <code>select</code> call.
Therefore, the filter clauses are needed to retain the good, and throw away the
bad objects. In addition, they give feedback to the generator for optimizing its
traversal priorities (as described in <a href="#gencl">Generat