2 - Use Case Diagrams
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Introduction to Use Case Diagrams
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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?
Is it a way to show how users interact with a computer program?
Exactly, Student_1! Use Case Diagrams visually represent the functional interactions between usersβreferred to as Actorsβand the system itself. Now, what do you think are the key components of these diagrams?
Actors and Use Cases?
Correct, Student_2! Actors represent external parties interacting with the system, while Use Cases denote the functionalities provided. Remember the acronym 'AUC'βActors, Use Cases, and the Boundaryβto help you recall these fundamental elements.
What does the system boundary do?
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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Now that we understand the components of Use Case Diagrams, letβs discuss their relationships. Who can explain the 'Include' relationship?
Is it when one Use Case includes another as part of its functionality?
Exactly right, Student_4! The 'Include' relationship signifies that one Use Case is always incorporated into another for shared processing. How about 'Extend'?
I think it's like adding optional features, right?
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?
Itβs like how some actors can inherit properties from a common actor?
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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Now that we've covered the fundamentals, letβs see how these diagrams apply in real-world scenarios. Imagine weβre working on an e-commerce site. What could our actors be?
I guess customers and admin staff?
Perfect! The actors would be the Customer and possibly the Admin. What about the Use Cases for a Customer?
Things like Register, Login, and Make Payment would definitely be included.
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?
It helps define system functionalities and validate requirements with stakeholders.
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
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
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.
Key Concepts
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Use Case Diagrams: Visual representation of interactions between users (actors) and systems.
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Actors: External parties engaging with the system.
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Use Cases: Functionalities that the system offers.
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System Boundary: Defines the scope of the system.
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Include Relationship: A mandatory use case included within another use case.
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Extend Relationship: Optional enhancements to a primary use case.
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Generalization: Inheritance among actors or use cases.
Examples & Applications
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
Interactive tools to help you remember key concepts
Rhymes
Actors and Use Cases in a diagram frame, visualizing interactions is the main aim.
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.
Memory Tools
To remember 'Actors, Use Cases, and System Boundary', think of 'A U C B'βlike a dance, where everyone's role is clear within the system.
Acronyms
Use 'I.E.G.' to remember
Include
Extend
Generalizationβrelationships defining our Use Cases!
Flash Cards
Glossary
- Actor
An external user or system that interacts with the application.
- Use Case
Specific functionalities that the system provides to meet user needs.
- System Boundary
An enclosure that defines what is included and excluded in a system.
- Include
A relationship where a Use Case always incorporates another Use Case.
- Extend
A conditional relationship where a Use Case may optionally enhance another Use Case.
- Generalization
A relationship that indicates inheritance among actors or Use Cases.
Reference links
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