title: XText Grammar rule for Abstract EMF Class
body: <p>I have an EMF metamodel containing Abstract Class <code>A</code> and Concrete Classes <code>B</code> &amp; <code>C</code> implement <code>A</code>.</p>
  <p>In XText I can have a rule such as <code>A: B | C;</code> and refer to A in other rules.</p>
  <p>Is there a way not to have to declare the rule for A and have a default rule used for abstract classes (which would be <code>OR(All concrete children)</code>) by Just providing the rules for <code>B</code> and <code>C</code>?</p>