title: How to make content exclusion in XSD?
body: <p>When defining an element in DTD, there is a feature to exclude elements from its content model, for example:</p>
  
  <pre><code>&lt;!ELEMENT i - - (%inline;) -(i)&gt;
  </code></pre>
  
  <p>Instead of repeating the content model for each element separately, we just list similar elements as a model group (entity in DTD) and exclude what we don't need in some elements.</p>
  
  <p>In XML Schema I can use complex types with inheritance and/or model groups to share the same content model between elements, but to exclude some elements I have to repeat the whole content model just not adding unwanted elements. Too much code to type, to read, to edit...</p>
  
  <p>Is there another, simple and beautiful way to implement this in XML Schema, or I should use RelaxNG or look for tools for generating schemas? Shortly, in XML Schema terminology, I want (and really need) something like derivation by restriction, but not duplicating the content model.</p>