Why URDF is not deprecated?

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Hi all,

I am following the tutorials on ROS and gazebo and I am really getting confused as to the current state of URDF and SDF.

The overall question is: if SDF supersedes URDF, why is URDF kept?

Now getting into details:

• You now need 2 descriptions of your scene (URDF and SDF)... Which is weird. Of course you can use gzsdf to do the conversion but
  1. It read the tool does not handle complex scenes,
  2. And you end up having to write a URDF with the hacky gazebo tags for simulation parameters rather than using the native SDF simulation parameters
• URDF is sometimes marked deprecated, sometimes you read there is no plan to get rid of it (here and here)
• SDF seems to only be supported in gazebo, what is the support state for SDF in MoveIt, RViz...and the other tools?
• When following the initial Gazebo tutorials, you are pushed to use SDF. Now when reaching the tutorials on the connection between ROS and gazebo they only talk about URDF, this is very misleading

Is this confusion due to a transitional state from URDF to SDF which last longer than expected, or is it supposed to last forever?

So what is the best practise today to use URDF and SDF on a large project? Should we specify things in URDF (including gazebo tags for links, joints and robots), convert to SDF using gzsdf and cross fingers that the gzsdf conversion works?

Thanks,

Antoine.