code: public void addEvaluatorDefinition( EvaluatorDefinition def ) {
          for ( String id : def.getEvaluatorIds() ) {
              this.evaluators.put( id,
                                   def );
          }
      }
docs: Adds an evaluator definition class to the registry. In case there exists
  an implementation for that evaluator ID already, the new implementation will
  replace the previous one.
  
  @param def the evaluator definition to be added.