/li>
</ul>
<p>
Generally, following <a href="https://tools.ietf.org/html/rfc760">Postel's law</a> is recommended:
</p>
<blockquote>
An implementation should be conservative in its sending behavior, and liberal in its receiving behavior.
</blockquote>
<p>
Applications should consider carefully how much validation beyond the security related issues to perform at run-time, and how errors will be handled.
</p>

<a name="schema"></a>
<h3>Using the XML schema</h3>

<p>
The XML schema can be used t