Refer to yuml.me site to understand how to represent uml diagram with text

You get three functions (for every sort of diagram) that you can map :

(global-set-key (kbd "C-c a") 'eyuml-create-activity-diagram)
(global-set-key (kbd "C-c c") 'eyuml-create-class-diagram)
(global-set-key (kbd "C-c u") 'eyuml-create-usecase-diagram)