A Use Case Diagram shows:

Actors (people or systems)
Use cases (what they do)
Connections between them

It’s a high-level functional map of responsibilities — perfect for explaining who triggers what and what’s available to whom.

📌 When to Use Use Case Diagrams

Use Case	Why It Helps
Explaining user roles	Shows clearly who can do what
Fiori app access planning	Maps apps to business users
BTP / UI5 app scope	Visualizes functions & actors
Business process overview	Bridges business and IT
Security / Authorization design	Starting point for role concept

🧩 Use Case Diagram Notation (PlantUML)

Element	Syntax	Meaning
Actor	`actor "User"`	A role (person or system)
Use case	`usecase "Do Something"`	A task or function
Connection	`User --> "Do Something"`	Actor is involved in the use case
Grouping	`package` or `rectangle`	Logical grouping of use cases
Alias	`usecase "Create Order" as UC1`	Optional short names for layout

✅ Example: Sales Process Roles

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@startuml
title Use Case Diagram — Sales Roles and Functions

actor "Sales Rep"
actor "Warehouse Clerk"
actor "Customer (External)" as Customer

usecase "Create Sales Order"
usecase "View Order Status"
usecase "Post Goods Issue"
usecase "Check Stock Availability"

"Sales Rep" --> "Create Sales Order"
"Sales Rep" --> "Check Stock Availability"
"Warehouse Clerk" --> "Post Goods Issue"
Customer --> "View Order Status"

@enduml

💡 You now clearly see:

Who does what
Which use cases are internal vs external
No deep logic, just role-to-action mapping

🔧 Another Example: Fiori App Scope

plantuml
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@startuml
title Use Case Diagram — Fiori App Access

actor "Purchasing Agent"
actor "Finance Clerk"

usecase "Manage Purchase Orders"
usecase "Display Supplier Info"
usecase "Approve Invoice"

"Purchasing Agent" --> "Manage Purchase Orders"
"Purchasing Agent" --> "Display Supplier Info"
"Finance Clerk" --> "Approve Invoice"

@enduml

This can feed directly into Fiori catalog design or role concepts.

🧠 Pro Tips

✅ Always define actors by role, not names

✅ Keep use case names functional: "Approve Invoice", not "ZFIAPP01"

✅ Use to align early with business stakeholders

✅ Great for kickoff, access planning, functional documentation

✅ Summary

Use case diagrams help you answer the core question:

Who does what?

Use them to:

Explain roles
Show system boundaries
Align business and technical stakeholders
Start from function before diving into process

Next up:

👉 Visual SAP #7 — C4 Model for SAP: Explain Architecture Without Overthinking

We’ll introduce the C4 model (Context + Container) and how to use it to explain your SAP system architecture in clear layers.

Visual SAP with plantUML #6 Use Case Diagrams