Are elements with mismatched prefixes allowed?
<p>The <a href="https://www.w3.org/TR/xml/#sec-common-syn" rel="nofollow">"Common Syntatic Constructs" section of the XML 1.0 Recommendation</a> contains the following note:</p>

<blockquote>
  <p>The Namespaces in XML Recommendation assigns a meaning to names
  containing colon characters. Therefore, authors should not use the
  colon in XML names except for namespace purposes, but <strong>XML processors
  must accept the colon as a name character.</strong></p>
</blockquote>

<p>This means that the following is invalid XML:</p>

<pre><code>&lt;xhtml:span
    xmlns:xhtml="http://www.w3.org/1999/xhtml"
    xmlns:html="http://www.w3.org/1999/xhtml"&gt;
  &lt;xhtml:a&gt;Anchor text&lt;/html:a&gt;
&lt;/xhtml:span&gt;
</code></pre>

<p>However, <a href="https://www.w3.org/TR/REC-xml-names/#ns-qualnames" rel="nofollow">the "Qualified Names" section of the Namespaces in XML Recommendation</a> contains this statement:</p>

<blockquote>
  <p>Note that the prefix functions only as a placeholder for a namespace
  name. <strong>Applications SHOULD use the namespace name, not the prefix</strong>,
  in constructing names whose scope extends beyond the containing
  document.</p>
</blockquote>

<p>This leads to an ambiguity. When something like this happens, does the XML recommendation have precedence, rendering the above document invalid, or should a namespace-aware XML processor first convert prefixes to their appropriate namespaces and consider the above document valid?</p>