ZenUML Sequence Diagram

Back to Style Guide — Read the style guide first for emoji, color, and accessibility rules.

Syntax keyword: zenuml Best for: Code-like sequence diagrams, method-call-style interactions, developers familiar with programming syntax When NOT to use: Prefer standard Sequence Diagrams for most use cases — ZenUML requires an external plugin and has limited GitHub support.

⚠️ GitHub support: ZenUML requires the @mermaid-js/mermaid-zenuml external module. It may not render on GitHub natively. Use standard sequenceDiagram syntax for GitHub compatibility.

⚠️ Accessibility: ZenUML does not support accTitle/accDescr. Always place a descriptive italic Markdown paragraph directly above the code block.

Exemplar Diagram

ZenUML sequence diagram showing a user authentication flow with credential validation and token generation using programming-style syntax:

zenuml
    @Actor User
    @Boundary AuthAPI
    @Entity Database

    // User initiates login
    User->AuthAPI.login(credentials) {
        AuthAPI->Database.findUser(email) {
            return user
        }
        if (user.valid) {
            return token
        } else {
            return error
        }
    }

Tips

• Uses programming-style syntax with method calls: A->B.method(args)
• Curly braces {} create natural nesting (activation bars)
• Control flow: if/else, while, for, try/catch/finally, par
• Participant types: @Actor, @Boundary, @Entity, @Database, @Control
• Comments with // render above messages
• return keyword draws return arrows
• Prefer standard sequenceDiagram for GitHub compatibility
• Use ZenUML only when the code-style syntax is specifically desired

Template

Description of the interaction flow:

zenuml
    @Actor User
    @Boundary Server
    @Entity DB

    User->Server.request(data) {
        Server->DB.query(params) {
            return results
        }
        return response
    }