UML Sequence Diagrams using PlantUML

June 9, 2019 #uml

I’ve blogged before about text notation for UML Sequence Diagrams in WebSequenceDiagrams notation, but since we standardize on Lucidchart for diagrams, I found they have UML Sequence Markup support as well.  However, Lucidchart’s dialect looks to be based on PlantUML.  For a better summary that I can provide, take please read Markdown native diagrams with PlantUML.  I decided to spin up the PlantUML docker image and take a look:

docker run -d -p 8080:8080 plantuml/plantuml-server:jetty

Because I love serverless, I used my ”google-fu” and found plantuml-render in the AWS Serverless Application Repository.  You can also try this interactively at

Even more exciting to me was that since I have Visual Studio Code support for both Markdown and PlantUML, this fenced code block rendered an image as expected.

title call flows  

participant a as "Aa"
participant b as "Bb"
participant c as "Cc"
participant d as "Dd"

a->b: sync call  
activate b
b->b: in process call
b->>c: async call  
activate c  
c-->b: 202 Accepted  
a<--b: return value  
deactivate b
c->d: background process  
deactivate c

UML Sequence Diagram

Later, I am going to think about the best way to check in this text-based UML next to our source code.  I haven’t figured out if the rendered images should be checked in as well, generated as part of a build, or just viewed as part of a markdown preview.

Kevin Hakanson

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