Visual SAP with plantUML #9 - How to Use ChatGPT to Generate Diagrams — From Prompt to PlantUML

Creating diagrams manually slows you down.

You know the process — but translating it into visuals takes time, formatting, and layout effort. With AI, you describe the flow in words, and ChatGPT turns that into a structured, readable, PlantUML diagram. You save hours.

ChatGPT helps you:

• Visualize processes from natural language

• Speed up documentation for functional specs or technical designs

• Generate clean PlantUML code you can preview, version, and reuse

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🧩 What You’ll Learn

• How to write effective prompts to generate diagrams

• What types of diagrams work best

• How to use structured input (like Excel)

• A library of ready-to-use prompts for SAP use cases

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✅ 1. What to Send as Input

The key to getting high-quality diagrams from AI is giving it structured context.

🧾 Your Prompt Should Include:

👉 You don’t need technical terms. Just be clear and linear.

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💬 Example Input

vbnet
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Generate a component diagram in PlantUML.
I have:
- A Fiori app that sends data to SAP PO
- SAP PO transforms and routes the message to S/4HANA
- Backend uses BAPI to post to HANA DB
Group into: Frontend, Middleware, Backend.

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⚙️ 2. Example Output from ChatGPT

plantuml
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@startuml
title SAP Integration — Component Diagram

package "Frontend" {
  component "Fiori App"
}

package "Middleware (SAP PO)" {
  component "iFlow"
  component "Mapping & Routing"
}

package "Backend (S/4HANA)" {
  component "SAP Gateway"
  component "BAPI Layer"
  component "HANA DB"
}

"Fiori App" --> "iFlow" : OData / SOAP
"iFlow" --> "Mapping & Routing"
"Mapping & Routing" --> "SAP Gateway"
"SAP Gateway" --> "BAPI Layer"
"BAPI Layer" --> "HANA DB"
@enduml

✅ Copy this into .puml and render it in VS Code or online.

You just saved 20–30 minutes of diagramming.

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🧰 3. Prompt Library — Use Case Templates

Here are prompt patterns you can reuse across SAP projects.

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🟦 ER Diagram

Prompt:

yaml
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Generate a PlantUML ER diagram for the following:
- MARA: MATNR (PK), MTART, MATKL
- MAKT: MATNR (FK to MARA), SPRAS, MAKTX
- MVKE: MATNR (FK to MARA), VKORG, VTWEG
Show relationships with cardinality.

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🟨 Activity Diagram

Prompt:

diff
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Create an activity diagram in PlantUML for:
- Creating a delivery
- Checking stock
- If stock is available, pick and post goods issue
- If not, notify the user
Add decisions and start/stop blocks.

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🟪 Sequence Diagram

Prompt:

diff
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Make a sequence diagram for:
- External system calls API Gateway
- Gateway triggers BAPI in S/4HANA
- S/4 processes and returns JSON
Use → for sync, →> for async

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🟩 Class Diagram

Prompt:

diff
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Class diagram in PlantUML:
- Controller class runs validation checks
- Interface IF_CHECK
- Two classes implement it: Check_Material, Check_Price
- Controller aggregates them and calls execute()

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🟥 Use Case Diagram

Prompt:

vbnet
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Use case diagram:
Actors: Purchasing Agent, Finance Clerk
Use Cases: Create PO, Display Supplier, Approve Invoice
Map actors to their actions.

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🟫 C4 Context Diagram

Prompt:

yaml
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C4 context diagram in PlantUML:
- Person: Sales Rep
- System: SAP S/4HANA
- External: CRM and SAP PO
Sales Rep uses S/4HANA
S/4 connects to CRM and PO
Use the C4 syntax and include titles.

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📊 4. Using Excel or Structured Input

Yes — you can go beyond plain text. Structured data makes diagrams better.

💡 Best Use Case: ER Diagram from Excel

Prompt:

pgsql
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Here is an Excel sheet with table definitions.
Generate a PlantUML ER diagram showing relationships.
Primary keys are marked 'Y'. Foreign keys map to other tables.

✅ You can attach or paste data as Markdown or CSV.

✅ ChatGPT will build the entities and relationships automatically.

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🧠 5. Best Practices

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✅ Summary

You don’t need to draw. You just need to describe.

ChatGPT will handle the rendering.

Use it to:

• Generate specs fast

• Align teams visually

• Avoid drawing everything by hand

• Keep documentation clear, live, and maintainable

The more structured your input → the better your diagram output.