Specify that id is explicitly for object class

msg/ObjectHypothesisWithPose.msg

@@ -1,8 +1,8 @@
 # An object hypothesis that contains position information.
 
-# The unique numeric ID of object detected. To get additional information about
-#   this ID, such as its human-readable name, listeners should perform a lookup
-#   in a metadata database. See vision_msgs/VisionInfo.msg for more detail.
+# The unique numeric ID of the object class. To get additional information about
+#   this ID, such as its human-readable class name, listeners should perform a
+#   lookup in a metadata database. See vision_msgs/VisionInfo.msg for more detail.
 int64 id
 
 # The probability or confidence value of the detected object. By convention,
@@ -17,4 +17,4 @@ float64 score
 #   parent messages.
 # Also note that different classes predicted for the same input data may have
 #   different predicted 6D poses.
-geometry_msgs/PoseWithCovariance pose
+geometry_msgs/PoseWithCovariance pose