code: public Object eval(Selector sel)
    {
      try
      {
        return eval(sel, MatchSpaceKey.DUMMY, EvalCache.DUMMY, null, false);
      }
      catch (BadMessageFormatMatchingException e)
      {
        // No FFDC Code Needed.
        // FFDC driven by wrapper class.
        FFDC.processException(this,
            cclass,
            "com.ibm.ws.sib.matchspace.selector.impl.Evaluator.eval",
            e,
            "1:145:1.28");
  //TODO: Pass "sel" in FFDC or merely trace?      
        // This truly does not happen (see MatchSpaceKey.DUMMY)
        throw new IllegalStateException(); // );
      }
    }
docs: Evaluates a selector tree without resolving identifiers (usually applied only to
  Selector subtrees with numIds == 0).
  
  @param sel the selector tree to evaluate
  
  @return the result, which will be a String, a BooleanValue, a NumericValue, or null.
  Null is used for "missing" Numeric or String values.  BooleanValue.NULL is used for
  missing Boolean values.