code: private void putToCache(final Element element, final Constraint object) {
  		String id = element.getAttributeValue(XMLTags.ID);
  		if (id != null && id.length() > 0) {
  			Constraint old = putToCache(id, object);
  			if (old != null) {
  				LOG.warn("The id=" + id + " for object of type=" + old.getClass().getName()
  						+ " was already found. Please make sure this is ok and no mistake.");
  			}
  		}
  	}
docs: If the element has an attribute with name id this attribute's value will be used as key to
  store the just generated object in a map. The object can in this case also be retrieved using
  this id.
  
  @see #getModel(String)