Commonly used messages in ROS. Includes messages for actions (actionlib_msgs), diagnostics (diagnostic_msgs), geometric primitives (geometry_msgs), robot navigation (nav_msgs), and common sensors (sensor_msgs), such as laser range finders, cameras, point clouds.
I wonder that why MODIFY is defined to be 0, which is also ADD defined to be. Is there an agenda? Or is it simply a mistake for "MODIFY=1"?
https://github.com/ros/common_msgs/blob/20a833b56f9d7fd39655b8491a2ec1226d2639b3/visualization_msgs/msg/Marker.msg#L17