docbook-xml software package provides standard XML documentation system for software and systems, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install docbook-xml
docbook-xml is installed in your system.
Make ensure the docbook-xml package were installed using the commands given below,
$ sudo dpkg-query -l | grep docbook-xml *
You will get with docbook-xml package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Text Processing |
| Package | docbook-xml |
| Version | 4.5-8 |
| Description | standard XML documentation system for software and systems |
| Sub Section | Text |