ixed - and this is usually difficult to test (and poorly tested)</li>
</ul>
<p>
On the other hand, validation during production use may be very important:
</p>
<ul>
 <li>Validation may be required for security reasons.  In particular, validation of narrative may be required to prevent active content or external references.</li>
 <li>Validating resources at specific control points in the data flow can allow for better detection and recovery as opposed to specific application logic failing on bad data<