Install dtdinst by entering the following commands in the terminal:
sudo apt update sudo apt install dtdinst
Description:
XML DTD to XML instance format converter
dtdinst converts XML DTDs into XML instance format. The XML instance can be in either a format specific to DTDinst or RELAX NG format.
Homepage: https://github.com/relaxng/jing-trang
Version: 20151127+dfsg-1
Section: universe/text