Requirements diagram

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A requirements diagram links requirements to the things that satisfy them and the tests that verify them. It is a SysML idea, and it is useful anywhere somebody will eventually ask "how do we know this works?".

The value is in the trace links, not in the boxes.

#When to reach for one

  • Regulated or safety-relevant work where traceability is required.

  • Complex features where requirements and components map many-to-many.

  • Audits, where the question is always which test covers which requirement.

#How to draw it in Capable

Route

Use when

PlantUML

Requirement-style diagrams with typed relationships.

draw.io

When the diagram is for a document rather than a model.

#A worked example

Requirements, what satisfies them, and what verifies them:

Requirements diagram

The source, which you can paste into a new diagram and edit:

@startuml
rectangle "REQ-1\nSessions expire after 30 minutes" as R1
rectangle "REQ-2\nExpiry is configurable" as R2
component "Session service" as S
component "Admin settings" as A
rectangle "TEST-14\nExpiry integration test" as T

R2 --> R1 : refines
S ..> R1 : satisfies
A ..> R2 : satisfies
T ..> R1 : verifies
@enduml

#A few things that catch people out

  • Name relationships properly. Satisfies, verifies and refines mean different things.

  • Give requirements stable identifiers; the diagram is worthless if the ids change.

  • Keep one diagram per feature. A whole-product requirements diagram is unreadable.

Cheap to change means it stays true.