> The best use case I can currently think of is to get rid of the geometry_msgs/FooWithCovariance message types and merge them into one geometry_msgs/Foo message with an optional covariance field While I agree that there may be valid use cases for optional fields, I don't think this is one of them. In a different robot framework that I regularly use, there is no `PoseStamped` message, only a `RigidBodyState`, which is the logical conclusion of what you propose and which has these fields: - position, cov_position - orientation, cov_orientation - velocity, cov_velocity - angular_velocity, cov_angular_velocity In contrast, I like the ROS messages (`Pose`, `PoseStamped`, `PoseWithCovariance` ...) better. The signature of the topic tells me immediately which fields are used or supposed to be filled. I don't have to do a `rostopic echo` or read the code to find out, and if they later decide to use a covariance, the API changes, so my code breaks and I know I have to adjust it. --- [Visit Topic](https://discourse.ros.org/t/optional-fields-in-message/991/7) 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: