Feature #7811
Updated by Reynaud Sylvain over 11 years ago
Example: 
 <pre><code class="xml"> 
 <argument name="arg" valid="view('accepted-values')/*/*[@value=$arg]"/> 
 </code></pre> 
 NOTE: This may replace attribute @pattern 
 <pre><code class="xml"> 
 <argument name="arg" valid="regexp:test($arg, 'my-regular-expression')"/> 
 </code></pre>