UML use case diagram implementation

Automatically layout use case diagrams from structured input. This is **VERY** useful in solution architecture.

This issue involves all conceptional work, that is needed to find a practical input format.

**UML Use Case Diagrams**.

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## 1. Actor Notation

* **Shape:** Stick figure
* **Placement:**
* Always **outside** the system boundary
* **Inheritance:**
* Solid line with **hollow triangle**
* Triangle points **to the parent actor**

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## 2. Use Case Notation

* **Shape:** Oval (ellipse)
* **Placement:**
* Always **inside** the system boundary
* **Inheritance:**
* Solid line with **hollow triangle**
* Triangle points **to the parent use case**

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## 3. System Boundary

* **Shape:** Rectangle
* **Contents:**
* Only use cases are allowed inside
* **Actors:**
* Never placed inside the boundary

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## 4. Association (Actor ↔ Use Case)

* **Line type:** Solid line
* **Arrowhead:** None (by default)
* **Connection:**
* Actor ↔ Use Case only

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## 5. «include» Relationship

* **Line type:** Dashed line
* **Arrowhead:** Open arrow
* **Direction:**
* From base use case → included use case
* **Label:**
* «include» (with guillemets)
* Placed near the line
* **Connection:**
* Use Case → Use Case only

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## 6. «extend» Relationship

* **Line type:** Dashed line
* **Arrowhead:** Open arrow
* **Direction:**
* From extending use case → base use case
* **Label:**
* «extend»
* **Optional:**
* Extension point name in brackets (rarely shown)

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## 7. Generalization (Inheritance)

Applies to **actors and use cases**.
* **Line type:** Solid line
* **Arrowhead:** Hollow triangle
* **Direction:**
* Child → Parent
* **Label:** None

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## 8. Visual Legend (Quick Reference)

| Element | Shape | Line | Arrow |
| -------------- | ------------ | ------ | --------------- |
| Actor | Stick figure | — | — |
| Use Case | Oval | — | — |
| System | Rectangle | — | — |
| Association | — | Solid | None |
| «include» | — | Dashed | Open |
| «extend» | — | Dashed | Open |
| Generalization | — | Solid | Hollow triangle |

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No file, test, or entry point is named. Start by reading the repository's existing diagram-generation APIs and UML-related support, then define a practical structured input format and verify that it can represent the listed actors, use cases, boundaries, and relationships.

Written by the indexing model from the issue text.