public boolean isDefault() {
    return isDefault == 0 ? false : true;
  }
Gets whether this is a default group and is mostly read-only. Default
groups cannot have their alert definition groupings changed. New alert
definitions are automtaically added to the default group that belongs to
the service of that definition.

@return {@code true} if this is a default group, {@code false} otherwise.
ambari-server/src/main/java/org/apache/ambari/server/orm/entities/AlertGroupEntity.java