Lecture 32: Factoring Use Cases - Managing Complexity with Relationships
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Introduction to Factoring Use Cases
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Welcome, everyone! Today we will explore the concept of Factoring Use Cases. Can anyone tell me what they think 'factoring' means in this context?
Is it about breaking down something into smaller pieces?
Exactly! Factoring involves breaking down large use cases into smaller, more manageable chunks. This helps us avoid redundancy and makes it easier to manage complexities. Why do we want to avoid redundancy?
To make our models clearer?
Correct! Clarity is key. If we keep repeating ourselves in multiple use cases, it can lead to confusion. Letβs remember: βLess repetition, more clarity!β
How do we actually factor the use cases?
Great question! We can use two specific relationships: <<include>> and <<extend>>. Let's dive into those!
<<include>> Relationship
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First, letβs talk about the <<include>> relationship. Can someone remind me about its purpose?
It shows a use case that must be included in another one?
Exactly! The behavior of the included use case is mandatory for the base use case. For example, if we have 'Place Order' as a use case, what included use case might we need?
Probably 'Log In' because you need to be logged in to place an order.
Right! We might say: 'Place Order <<include>> Log In'. This way, we donβt repeat 'Log In' in both use cases. Can anyone summarize why using <<include>> is beneficial?
It avoids repeating details and makes it clear that 'Log In' is necessary!
<<extend>> Relationship
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Next, let's move to the <<extend>> relationship. Does anyone know what that signifies?
Itβs for optional behaviors that get added under certain conditions?
Very well said! For instance, when might we use an <<extend>> relationship in our online shopping example?
When applying a discount coupon, right? That wouldn't happen every time someone places an order.
Correct! We can write: 'Place Order <<extend>> Apply Discount Coupon' with the extension point defined after cart total calculation. How is this beneficial for us?
It keeps our primary use case simple while allowing for flexibility!
Generalization for Actors
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Now, let's talk about using generalization for actors. Letβs define what generalization means in this context.
Itβs about showing how one actor is a specific type of another actor?
Exactly! For instance, if we say 'Manager ---|> Employee', what does this imply?
A manager is a type of employee and inherits the roles or capabilities of an employee.
Right! Generalization helps us capture common behaviors in actors efficiently. Any thoughts on when you would use this?
In systems where several roles share similar functionalities, it can reduce complexity!
Best Practices for Factoring Use Cases
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To wrap up our session, let's discuss best practices for factoring use cases. What do you think we should keep in mind?
Donβt over-factor! We should only do it when it really helps.
Absolutely! We should ensure that even factored use cases represent complete goals for the users. Also, what about extension points when using <<extend>>?
They should be clearly defined so it's understandable where additional behavior fits in.
Exactly! So remember: 'Clarity, reusability, and goal orientation' are our keys in maintaining effective use cases.
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
The lecture covers the necessity and benefits of factoring use cases, explaining how the include and extend relationships can simplify large use cases and promote code reusability. Students will learn to differentiate between these relationships and understand the implications of generalization for actors.
Detailed
Detailed Summary
This lecture builds upon foundational concepts in Use Case Modeling, specifically by introducing the idea of Factoring Use Cases through relationships defined in the Unified Modeling Language (UML). The main need for factoring use cases arises from common issues such as redundancy and complexity in large use cases. Factoring helps in reusing common functionalities, distinguishing between core and optional behaviors, and ultimately enhancing the overall clarity of the Use Case Models.
Key Concepts:
- The Need for Factoring Use Cases:
- Avoid redundancy by allowing common functionalities to be captured only once.
- Help manage complexity by breaking down large use cases into more manageable segments.
- Promote reusability of common or optional behaviors.
- Relationships Between Use Cases:
- The <
> Relationship : Mandatory inclusion of one use case within another, indicated by a dashed arrow and used to avoid redundancy. - The <
> Relationship : Represents optional or conditional behavior that adds new functionality into a base use case, allowing for specific conditions to direct the flow. - Generalization for Actors: Useful for representing commonalities among various roles in the system.
- Best Practices of Factoring Use Cases: Emphasize clarity and balance in the Use Case Model without over-factoring.
Understanding these relationships gives developers tools to create clearer, more maintainable software requirements.
Key Concepts
-
The Need for Factoring Use Cases:
-
Avoid redundancy by allowing common functionalities to be captured only once.
-
Help manage complexity by breaking down large use cases into more manageable segments.
-
Promote reusability of common or optional behaviors.
-
Relationships Between Use Cases:
-
The <
> Relationship : Mandatory inclusion of one use case within another, indicated by a dashed arrow and used to avoid redundancy. -
The <
> Relationship : Represents optional or conditional behavior that adds new functionality into a base use case, allowing for specific conditions to direct the flow. -
Generalization for Actors: Useful for representing commonalities among various roles in the system.
-
Best Practices of Factoring Use Cases: Emphasize clarity and balance in the Use Case Model without over-factoring.
-
Understanding these relationships gives developers tools to create clearer, more maintainable software requirements.
Examples & Applications
A user must 'Log In' before they can 'Place Order'; hence, we factor 'Log In' into both using the <
Applying a 'Discount Coupon' is optional and can be added after calculating the total in the 'Place Order' use case using the <
In an organization, a Manager is an actor that inherits roles from the general Actor 'Employee' showcasing generalization.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
If things are too big, break them down,
Stories
Imagine a chef making a grand meal. If he includes a common recipe for sauces in every dish, he saves time and avoids confusion. This is like using <
Memory Tools
I.E. (Include - Extend) - 'Include to add necessary depth, Extend to add the optional breadth.'
Acronyms
F.C.R. - 'Factoring Cuts Redundancy' to remember that factoring helps avoid repetition.
Flash Cards
Glossary
- <<include>> Relationship
A mandatory inclusion where one use case's behavior must be incorporated into another use case.
- <<extend>> Relationship
An optional extension of a use case behavior that occurs under specific conditions.
- Factoring Use Cases
The process of breaking down larger use cases into smaller, reusable components to avoid redundancy and manage complexity.
- Generalization
A relationship that shows how one actor (subclass) is a specialized form of another actor (superclass).
- Extension Point
A defined location in a use case that allows for the inclusion of extending behavior.
Reference links
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