2 - Use Case Diagrams

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Introduction to Use Case Diagrams

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Teacher
Teacher

Welcome, students! Today, we're diving into Use Case Diagrams, which are essential for understanding how users interact with a system. Can anyone describe what a Use Case Diagram is?

Student 1
Student 1

Is it a way to show how users interact with a computer program?

Teacher
Teacher

Exactly, Student_1! Use Case Diagrams visually represent the functional interactions between users—referred to as Actors—and the system itself. Now, what do you think are the key components of these diagrams?

Student 2
Student 2

Actors and Use Cases?

Teacher
Teacher

Correct, Student_2! Actors represent external parties interacting with the system, while Use Cases denote the functionalities provided. Remember the acronym 'AUC'—Actors, Use Cases, and the Boundary—to help you recall these fundamental elements.

Student 3
Student 3

What does the system boundary do?

Teacher
Teacher

Great question, Student_3! The system boundary encapsulates the Use Cases, demonstrating the scope of the system. To summarize, Use Case Diagrams help us visualize how users like customers and administrators interact with the system. It's all about capturing high-level requirements.

Relationships in Use Case Diagrams

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Teacher
Teacher

Now that we understand the components of Use Case Diagrams, let’s discuss their relationships. Who can explain the 'Include' relationship?

Student 4
Student 4

Is it when one Use Case includes another as part of its functionality?

Teacher
Teacher

Exactly right, Student_4! The 'Include' relationship signifies that one Use Case is always incorporated into another for shared processing. How about 'Extend'?

Student 1
Student 1

I think it's like adding optional features, right?

Teacher
Teacher

Spot on! The 'Extend' relationship introduces optional behavior that can enhance the primary functionality based on conditions. Now, let's chat about 'Generalization'. What does it mean?

Student 2
Student 2

It’s like how some actors can inherit properties from a common actor?

Teacher
Teacher

Exactly! Generalization captures inheritance, which helps us streamline actors and use cases by showing hierarchical relationships. Excellent job, class! Remember these relationships with the acronym 'IEG': Include, Extend, Generalization.

Practical Application of Use Case Diagrams

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Teacher
Teacher

Now that we've covered the fundamentals, let’s see how these diagrams apply in real-world scenarios. Imagine we’re working on an e-commerce site. What could our actors be?

Student 3
Student 3

I guess customers and admin staff?

Teacher
Teacher

Perfect! The actors would be the Customer and possibly the Admin. What about the Use Cases for a Customer?

Student 4
Student 4

Things like Register, Login, and Make Payment would definitely be included.

Teacher
Teacher

Exactly right! Use Cases such as Search Product, Add to Cart, and Checkout would also be included. Now, why is it important for a Business Analyst to use these diagrams early in the discovery phase?

Student 1
Student 1

It helps define system functionalities and validate requirements with stakeholders.

Teacher
Teacher

Yes, it aids in aligning everyone involved and improving communication. As a quick summary, Use Case Diagrams provide clarity on functionalities and user interactions, making them indispensable tools for BAs.

Introduction & Overview

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Quick Overview

Use Case Diagrams provide a high-level perspective on system functionalities and interactions between users and the system.

Standard

Use Case Diagrams focus on external interactions between actors and the system, defining functionalities through clear visual representations. They help business analysts outline the scope of a system and validate requirements with stakeholders.

Detailed

Use Case Diagrams

Use Case Diagrams are a key element of Unified Modeling Language (UML) that visually represent the functional interactions of actors (users or systems) with a software system. They serve several crucial purposes in software development, such as defining the scope of the system and highlighting its capabilities. Key components in these diagrams include Actors, Use Cases, and relationships among them, such as Include, Extend, and Generalization. These diagrams are instrumental for Business Analysts (BAs) as they validate functional scope and clarify user roles.

Key Components of Use Case Diagrams:

  • Actors: External users or systems engaging with the software.
  • Use Cases: Functionalities provided by the system.
  • System Boundary: Encapsulates use cases to depict the scope of the software.

Relationships:

  • Include: A use case incorporating another use case for shared functionality.
  • Extend: A use case that has optional extensions based on a condition.
  • Generalization: Inheritance relationships among actors or use cases.

Example:

In an e-commerce platform, the primary Actor is the Customer with Use Cases including Register, Login, Search Product, Add to Cart, Checkout, and Make Payment. The diagram illustrates these interactions, aiding BAs in defining system functionality and understanding user goals.

Definitions & Key Concepts

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Key Concepts

  • Use Case Diagrams: Visual representation of interactions between users (actors) and systems.

  • Actors: External parties engaging with the system.

  • Use Cases: Functionalities that the system offers.

  • System Boundary: Defines the scope of the system.

  • Include Relationship: A mandatory use case included within another use case.

  • Extend Relationship: Optional enhancements to a primary use case.

  • Generalization: Inheritance among actors or use cases.

Examples & Real-Life Applications

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Examples

  • In an e-commerce application, a 'Customer' actor can perform several use cases such as 'Register', 'Login', and 'Checkout'.

  • A 'Library System' could have actors like 'Member' and 'Librarian', with use cases such as 'Borrow Book' and 'Return Book'.

Memory Aids

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🎵 Rhymes Time

  • Actors and Use Cases in a diagram frame, visualizing interactions is the main aim.

📖 Fascinating Stories

  • Imagine a bustling marketplace: Actors, such as Customers and Sellers, explore the stalls (Use Cases) to find what they need to buy or sell. This story helps us see how the marketplace is organized, mirroring a use case diagram.

🧠 Other Memory Gems

  • To remember 'Actors, Use Cases, and System Boundary', think of 'A U C B'—like a dance, where everyone's role is clear within the system.

🎯 Super Acronyms

Use 'I.E.G.' to remember

  • Include
  • Extend
  • Generalization—relationships defining our Use Cases!

Flash Cards

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Glossary of Terms

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  • Term: Actor

    Definition:

    An external user or system that interacts with the application.

  • Term: Use Case

    Definition:

    Specific functionalities that the system provides to meet user needs.

  • Term: System Boundary

    Definition:

    An enclosure that defines what is included and excluded in a system.

  • Term: Include

    Definition:

    A relationship where a Use Case always incorporates another Use Case.

  • Term: Extend

    Definition:

    A conditional relationship where a Use Case may optionally enhance another Use Case.

  • Term: Generalization

    Definition:

    A relationship that indicates inheritance among actors or Use Cases.