code: public static SubTaskStrategy getSubTaskStrategy(String attributeValue, Long processInstanceId) throws StrategyException {
          Package packageVO = processInstanceId == null ? null : getPackage(processInstanceId);
          TaskInstanceStrategyFactory factory = getInstance();
          String className = factory.getStrategyClassName(attributeValue, StrategyType.SubTaskStrategy);
          SubTaskStrategy strategy = (SubTaskStrategy) factory.getStrategyInstance(SubTaskStrategy.class, className, packageVO);
          return strategy;
      }
docs: Returns a subtask strategy instance based on an attribute value and bundle spec
  which can consist of either the subtask strategy logical name, or an xml document.
  @param attributeValue
  @return the subtask strategy implementor instance