As for a direct use case, we ran into one recently when wanting to write a ROStful (ROS-REST conversion interface) client. As a client to a REST server api, it may need to set outgoing optional fields and parse incoming optional fields. A fixed ros message is not rich enough to transmit/receive this kind of information. --- [Visit Topic](https://discourse.ros.org/t/optional-fields-in-message/991/6) or reply to this email to respond. If you do not want to receive messages from ros-users please use the unsubscribe link below. If you use the one above, you will stop all of ros-users from receiving updates. ______________________________________________________________________________ ros-users mailing list ros-users@lists.ros.org http://lists.ros.org/mailman/listinfo/ros-users Unsubscribe: