Thank you for your support!
We have successfully created our own action to insert URN.
Basically in 16.0 we do not have support for URN, we have got the below support from you
One possible workaround for the client:
If in the Eclipse Preferences->oXygen->"Document Type Association" page you edit the "DITA" document type, in the "Validation" tab you can edit the "DITA" validation scenario and remove from it the third stage
(engine: DITA Validation).
Now we would like to know which schema file will be used for this DITA Validation since we do not want to remove that complete "DITA Validation" as it may contain other needed validations.
Could you please help us in Supporting URN without following this workaround.
Thanks in advance!