title: How default is the default encoding (UTF-8) in the XML Declaration?
body: <p>I know that <a href="http://www.w3.org/TR/xml/#charencoding" rel="nofollow noreferrer">the default encoding of XML is UTF-8</a>. All XML consumers MUST and so on and so forth. So this is not just a question whether or not XML has a default encoding.</p>
  
  <p>I also know that <a href="http://www.w3.org/TR/REC-xml/#sec-prolog-dtd" rel="nofollow noreferrer">the XML-Declarataion <code>&lt;?xml version="1.0" ... ?&gt;</code></a> at the beginning of the document itself is optional. And that specifying the encoding therein is optional as well.</p>
  
  <p>So I ask myself if the following two XML-Declarations are two expressions for the exact same thing:</p>
  
  <pre><code>&lt;?xml version="1.0"?&gt;
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  </code></pre>
  
  <p>From my own current understanding I would say those are equivalent but I do not <em>know</em>. 
  Has the equivalence of these two declarations been specified somewhere?</p>
  
  <p>(Consider these two example lines being each the first line of an XML document, preceded by any (zero) bytes and being UTF-8 encoded)</p>