You can vote to improve syntax about packages/namespaces !

There are several ways to use PlantUML and Emacs together :

 

 

Emacs

From the original work by Zhang Weize, plantuml-mode supports editing and previewing PlantUML diagrams all within Emacs, optionally also integrating with Org-Babel.

Luca Greco has shared a set of standalone helpers to edit, render, preview PlantUML code from Emacs.

 

 

Org-Babel

Org-Babel now natively supports blocks of plantuml code.

 

 

Emacs Org-Mode

You can also use PlantUML with Emacs org-mode.

You will find the needed macro at the following address http://www.emacswiki.org/emacs/IanYang

Once installed, embed PlantUML code in Emacs org-mode is used like this:

#+BEGIN_UML
Alice -> Bob: Authentication Request
Bob --> Alice: Authentication Response
#+END_UML

While the org file is exported to HTML or other formats, PlantUML is called to generate image and replace the block in place.

Thanks to Ian Yang for the work done.

This method, however, is considered obsolete:

;; OBSOLETED, use ob-plantuml.el bundled in org instead.

( A citation from https://www.emacswiki.org/emacs/org-export-blocks-format-plantuml.el )

---