title: What is an XML infoset and in what ways is it different to an XML document?
body: <p>I've tried to read <a href="http://www.w3.org/TR/xml-infoset/" rel="noreferrer">http://www.w3.org/TR/xml-infoset/</a> and the <a href="http://en.wikipedia.org/wiki/XML_Information_Set" rel="noreferrer">wikipedia entry</a>. But frankly I'm still not sure what the difference is.</p>
  
  <p>The quote :</p>
  
  <blockquote>
    <p>An XML document has an information set
    if it is well-formed and satisfies the
    namespace constraints. There is no
    requirement for an XML document to be
    valid in order to have an information
    set.</p>
  </blockquote>
  
  <p>From the wikipedia entry seems to not make sense. How can a non valid document have any semantics, and thus how can it be an 'information' set? </p>
  
  <p>What is this 'infoset' that  </p>
  
  <blockquote>
    <p>well-formed and satisfies the namespace constrained</p>
  </blockquote>
  
  <p>XML has? And in what way it is useful in itself. In other words why is it, semantically speaking, necessary to define the <strong>XML</strong> infoset? Is there any information that cannot be  represented in XML? If so I can see the limiting set of the XML Infoset, but if not surely the XML Infoset is as meaningless as term 'information'?  </p>
  
  <p><strong>Thank you for the interesting answers:</strong>
  <em>I still cannot grasp why the Xml infoset has any purpose as opposed to the term infoset. But you guys  have given me the direct answer to the question</em>.</p>