Use case diagrams in Software Engineering - Step-by-Step Execution

Concept Flow - Use case diagrams

Identify Actors

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Identify Use Cases

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Draw Actors and Use Cases

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Connect Actors to Use Cases

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Add Relationships (include, extend)

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Review Diagram for Completeness

The flow shows how to create a use case diagram step-by-step from identifying actors to reviewing the final diagram.

Execution Sample

Software Engineering

Actors: Customer, Admin
Use Cases: Login, Purchase, Manage Inventory
Connections: Customer->Login, Customer->Purchase, Admin->Manage Inventory

This example lists actors and use cases, then shows how actors connect to use cases in a use case diagram.

Analysis Table

Step	Action	Details	Result
1	Identify Actors	Customer, Admin	Actors listed
2	Identify Use Cases	Login, Purchase, Manage Inventory	Use cases listed
3	Draw Actors and Use Cases	Actors as stick figures, Use cases as ovals	Basic diagram shapes created
4	Connect Actors to Use Cases	Customer->Login, Customer->Purchase, Admin->Manage Inventory	Relationships drawn
5	Add Relationships	Include 'Login' in 'Purchase'	Diagram shows include relationship
6	Review Diagram	Check all actors and use cases connected	Diagram complete and clear
7	End	All steps done	Use case diagram ready

💡 All actors and use cases identified and connected, diagram reviewed and finalized

State Tracker

Element	Start	After Step 1	After Step 2	After Step 4	After Step 5	Final
Actors	None	Customer, Admin	Customer, Admin	Customer, Admin	Customer, Admin	Customer, Admin
Use Cases	None	None	Login, Purchase, Manage Inventory	Login, Purchase, Manage Inventory	Login, Purchase, Manage Inventory	Login, Purchase, Manage Inventory
Connections	None	None	None	Customer->Login, Customer->Purchase, Admin->Manage Inventory	Include: Login in Purchase	All connections drawn

Key Insights - 3 Insights

Why do we identify actors before use cases?

Actors represent who interacts with the system, so knowing them first helps define what actions (use cases) they perform, as shown in execution_table step 1 and 2.

What does the 'include' relationship mean in a use case diagram?

It means one use case always uses another as part of its process, like 'Purchase' includes 'Login' in step 5 of the execution_table.

Can an actor connect to multiple use cases?

Yes, actors can interact with many use cases, for example, 'Customer' connects to both 'Login' and 'Purchase' in step 4.

Visual Quiz - 3 Questions

Look at the execution_table at step 4, which actor connects to 'Manage Inventory'?

A Admin

B Both Customer and Admin

C Customer

D No actor connects

💡 Hint

Check the 'Connections' column at step 4 in the execution_table

At which step does the diagram show the 'include' relationship?

A Step 3

B Step 4

C Step 5

D Step 6

💡 Hint

Look for 'Add Relationships' action in the execution_table

If we add a new actor 'Guest' who only logs in, which step would change?

A Step 1 only

B Steps 1 and 4

C Step 5 only

D No steps change

💡 Hint

Adding an actor affects actor list and connections, see variable_tracker and execution_table steps 1 and 4

Concept Snapshot

Use case diagrams show system users (actors) and their actions (use cases).
Actors are drawn as stick figures; use cases as ovals.
Connect actors to use cases with lines.
Use 'include' to show one use case uses another.
Helps understand system requirements visually.

Full Transcript

Use case diagrams visually represent how users interact with a system. The process starts by identifying actors, who are the users or external systems. Next, identify use cases, which are the actions or services the system provides. Then, draw actors as stick figures and use cases as ovals. Connect actors to the use cases they interact with using lines. Add relationships like 'include' to show when one use case is part of another. Finally, review the diagram to ensure it clearly shows all interactions. This step-by-step approach helps create clear and useful diagrams for understanding system behavior.