<strong>Multiple declaration 
  </strong> </p>
<p>Some BNF variants allow multiple declarations of a <tt>rule</tt>. The declarations 
  are taken as alternatives. Example:</p>
<pre>
   <span class=identifier><code>r </code></span><code><span class=special>= </span><span class=identifier>a</span><span class=special>;    </span><span class=identifier>
   r </span><span class=special>= </span><span class=identifier>b</span><span class=special>;</span></code></pre>
<p> is equivalent to: </p>
<pre>
   <span clas