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Mermaid Requirement Diagram

Trace requirements to the elements that satisfy and verify them (SysML).

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Basic requirement diagram example

Basic requirement diagram example diagram
mermaid
requirementDiagram
    requirement login_req {
      id: 1
      text: Users must log in with email and password
      risk: high
      verifymethod: test
    }
    performanceRequirement speed_req {
      id: 1.1
      text: Login completes in under 1 second
      risk: medium
      verifymethod: analysis
    }
    element auth_service {
      type: service
    }
    element login_tests {
      type: "test suite"
    }
    auth_service - satisfies -> login_req
    login_tests - verifies -> login_req
    speed_req - derives -> login_req
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Requirement diagrams come from SysML and show requirements, the system elements that satisfy them, and how they're verified. They're useful in regulated industries and anywhere traceability matters.

Each requirement has an id, text, risk level and verification method; relationships like satisfies, verifies, traces and derives connect everything together.

When to use a requirement diagram

  • Traceability for regulated software (medical, automotive)
  • Systems engineering
  • Acceptance criteria mapping
  • Test coverage of requirements

Requirement Diagram syntax reference

SyntaxWhat it does
requirementDiagramStart a requirement diagram.
requirement name { id: … text: … risk: … verifymethod: … }Define a requirement.
functionalRequirement / performanceRequirement / interfaceRequirement / physicalRequirement / designConstraintRequirement subtypes.
risk: low | medium | highRisk level.
verifymethod: analysis | inspection | test | demonstrationHow it is verified.
element name { type: … }A system element.
a - satisfies -> bRelationship: contains, copies, derives, satisfies, verifies, refines, traces.

Requirement Diagram examples

Tips and best practices

  • Use hierarchical ids (1, 1.1, 1.2) to mirror your requirements document.
  • Keep requirement text short and testable.
  • Model test suites as elements with verifies relationships to show coverage.

Generate a requirement diagram with AI

Not sure where to start? Describe what you need and the AI requirement diagram generator writes the Mermaid code for you. Try prompts like:

  • “Requirements for a password reset feature”
  • “Safety requirements for an insulin pump”
  • “Requirements for a payment API”

Requirement Diagram templates

Password Reset Requirements

Requirement diagram linking password reset requirements to the services and tests that satisfy and verify them.

Requirement Diagram FAQ

What relationships can a Mermaid requirement diagram show?

contains, copies, derives, satisfies, verifies, refines and traces, written as source - relationship -> target.

When should I use a requirement diagram instead of a table?

When relationships matter — for example to show which tests verify which requirements, or how a performance requirement derives from a functional one.