code: protected void addModelReference(XAttributable object, SXTag target)
  			throws IOException {
  		XAttributeLiteral modelRefAttr = (XAttributeLiteral) object
  				.getAttributes().get(XSemanticExtension.KEY_MODELREFERENCE);
  		if (modelRefAttr != null) {
  			target.addAttribute("modelReference", modelRefAttr.getValue());
  		}
  	}
docs: Helper method, adds all model references of an attributable to the given
  tag.
  
  @param object
  Attributable element.
  @param target
  Tag to add model references to.