I learned how to correctly read sequence diagrams. I came across a recent post that suggests “Sequence diagrams are the only good thing UML brought to software development”. I’d never thought they were that useful but it turns out that was because I’d been misreading them.
There’s probably been a few instances over the years where I’ve made a flowchart where a sequence diagram would have been better. For example, I tend to add a high-level overview of how a request moves through our application especially since Mermaid.js makes it really easy to add to markdown documentation (Github and Azure DevOps will both render them).
Here’s a quick example of a typical vertical slice architecture we would use at Headspring. Adding this code block to a markdown file will render a sequence diagram using Mermaid:
sequenceDiagram
UI->>api: http request
participant api as API controller
Note over UI,api: This gets bound to a viewModel <br/>(*[Query|Command].cs)
participant mediatr as Mediatr handler
api->>mediatr: Mediatr request
mediatr->>DB: Entity framework query
DB-->>mediatr: DB records
Note over mediatr: Business logic/validation
mediatr-->>api: Response data
Note over api,mediatr: viewModel (*[Response|Command].cs)
api-->>UI: http response
Rendered on Github:
