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Introduction to Cohesion
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Today, weβre going to discuss cohesion in software design. Cohesion measures how closely related the responsibilities of a single module are. Can anyone tell me why high cohesion is beneficial?
It makes it easier to maintain because everything related is in one place.
Exactly! Higher cohesion enhances maintainability and reduces complexity. Anyone else?
Does high cohesion help with reusability too?
Yes! Modules with clear, single purposes are more likely to be reused in different contexts. Great insight!
What kinds of cohesion are there?
Great question! Cohesion can be categorized from functional to coincidental, each with varying levels of desirability. We'll go over those details shortly.
Remember: Cohesion relates to the 'singleness of purpose' of a module. Let's summarize: High cohesion boosts maintainability, reusability, and reduces complexity.
Types of Cohesion
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Now, letβs dive into the types of cohesion. Can someone name the highest form of cohesion?
Functional Cohesion, where every part of the module contributes to a single function!
Correct! Functional cohesion is ideal because it means the module is focused on one task. How about the next type?
Sequential Cohesion! That's where the output from one part serves as input to the next part.
Exactly! What about communicational cohesion?
Itβs when elements use common data but perform different functions.
Right! Recall these definitions for your quizzes. Letβs summarize: Functional, Sequential, and Communicational are the top three types of cohesion to look for in design.
Strategies for Achieving High Cohesion
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To achieve high cohesion, what strategies do you think can be employed?
We can break down larger modules into smaller ones with more focused responsibilities.
Exactly! By breaking down modules, we create focused segments that handle specific tasks or responsibilities. What else can we do?
We could aim for functional, sequential, or communicational cohesion.
Great thought! Striving for those types of cohesion is key in design. Remember, high cohesion often aligns with low coupling. They work best together.
Cohesion and Coupling Relationship
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Letβs talk about how cohesion relates to coupling. What do you understand about their relationship?
Higher cohesion usually results in lower coupling, right?
Correct! High cohesion means modules are self-contained and less dependent on others. How does that affect the system?
It makes the system more flexible and maintainable! Changes in one module wonβt easily impact others.
Exactly! Less interdependency leads to lower risks when modifying system modules. Remember, high cohesion and low coupling are the golden rules for robust design.
Introduction & Overview
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Quick Overview
Standard
Cohesion is a measure of how related and focused the responsibilities of a single module are in software design. Higher cohesion promotes maintainability and reusability, while lower cohesion leads to complexity and difficulties in understanding module functions. The section also categorizes cohesion types, emphasizing that functional, sequential, and communicational cohesion are the most desirable.
Detailed
Achieving High Cohesion
Cohesion refers to the degree to which the elements within a software module belong together. It is a critical quality attribute in software design, ensuring that modules are easier to maintain, test, and understand.
Importance of Cohesion
- Maintainability: Highly cohesive modules have functionalities that are closely related, which reduces the likelihood of unintended side effects when modifications occur.
- Reusability: Modules designed with a single, clear purpose can be reused in different contexts effectively.
- Understandability: Simplifying a moduleβs purpose makes it easier for developers to grasp its function.
- Reduced Complexity: Cohesive modules minimize interdependencies, lowering overall complexity.
Types of Cohesion (Best to Worst)
- Functional Cohesion: Every element contributes to a single, well-defined function. (Ideal)
- Sequential Cohesion: The output from one part serves as input to another, maintaining a sequence that serves a single purpose. (High)
- Communicational Cohesion: All elements operate on the same data, providing different functions while sharing common data. (High)
- Procedural Cohesion: Activities are grouped by the sequence they must follow, regardless of their functional connection. (Medium)
- Temporal Cohesion: Actions are related by timing rather than function, such as initializing components at startup. (Low)
- Logical Cohesion: Elements perform logically related activities but are distinct in functionality. (Very Low)
- Coincidental Cohesion: Elements are grouped randomly, showing no meaningful relationship. (Worst)
Achieving High Cohesion
To achieve high cohesion, designers should focus on:
- Functional, Sequential, or Communicational Cohesion when structuring modules.
- Breaking down large modules into smaller, focused segments, each with a single well-defined responsibility.
Recognizing the relationship between cohesion and coupling is paramount; high cohesion often leads to low coupling, creating a robust and maintainable software architecture.
Audio Book
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Design Principle of High Cohesion
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Design Principle: Strive for Functional, Sequential, or Communicational Cohesion. Avoid Logical and Coincidental.
Detailed Explanation
This chunk emphasizes the importance of aiming for three main types of cohesionβFunctional, Sequential, and Communicationalβwhen designing software modules. Strong cohesion is essential because it means that the elements of a module are related by a clear purpose, leading to easier maintenance and enhanced reusability. In contrast, Logical and Coincidental cohesion are the least desirable as they indicate weak relationships among module components.
Examples & Analogies
Think of a good sports team, where each player has a defined role that supports the team's success. For example, in soccer, a forward scores goals, while a defender prevents goals. If players are working toward specific, clear objectives (like scoring or defending), they perform better as a cohesive unit. However, if players are just randomly doing tasks without clear roles (like all trying to defend and no one to score), the team's success is compromised, similar to modules with low cohesion.
Strategies for Achieving High Cohesion
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Strategies: Break down large modules with low cohesion into smaller, more focused modules. Each module should have a single, well-defined responsibility.
Detailed Explanation
This chunk outlines strategies for achieving high cohesion by emphasizing the need to minimize large, unfocused modules. This can be accomplished by decomposing them into smaller modules, each dedicated to a specific chunk of functionality. This approach clarifies the purpose and enhances maintainability, since developers can make changes in one module without impacting others.
Examples & Analogies
Consider a restaurant. Instead of having one person cook, serve, and clean (a single large module), it's more efficient to have separate staff for each task (small focused modules). The chef specializes in cooking, the waitstaff in serving, and the cleaning crew in maintaining cleanliness. This separation leads to better performance in each role and, overall, a smoother operation.
Relationship Between High Cohesion and Low Coupling
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Relationship with Coupling: High cohesion often goes hand-in-hand with low coupling.
Detailed Explanation
This chunk discusses the interconnectedness of high cohesion and low coupling in software design. High cohesion enhances a module's focus and clarity, whereas low coupling reduces dependencies between modules. Therefore, aiming for both high cohesion and low coupling generally results in a more maintainable and understandable software architecture.
Examples & Analogies
Think of a well-organized library. Each section (like fiction, non-fiction, biographies) is self-contained (high cohesion) but doesnβt rely on the other sections to function (low coupling). Readers can easily browse a section without needing to look in others, creating an experience where all resources are clear and accessible with minimal confusion between sections.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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Cohesion: Refers to the closeness of relatedness of module functionalities.
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Types of Cohesion: Categories of cohesion include functional, sequential, communicational, procedural, temporal, logical, and coincidental.
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Achieving High Cohesion: Strategies include module breakdown and focusing on certain types.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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A module 'CalculateTotalIncome()' that adds incomes from different sources implements functional cohesion because all its parts work towards one output.
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A module 'ProcessPayment()' that first checks account balance, then deducts an amount, and finally sends a confirmation utilizes sequential cohesion as each step depends on the previous.
Memory Aids
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π΅ Rhymes Time
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Cohesion is key, tight and all right, makes your code easy, clear, and bright!
π Fascinating Stories
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Imagine a restaurant kitchen where each chef is responsible for a single dish. They pass on their ingredients to the next chef like a relay - thatβs high cohesion, keeping everyone specialized!
π§ Other Memory Gems
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Funky Stephen Can Play To Loudly Collaboration β (F: Functional, S: Sequential, C: Communicational, P: Procedural, T: Temporal, L: Logical, C: Coincidental)
π― Super Acronyms
FSCPLCC β Remember this acronym for the order of the cohesion types from best to worst.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
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Term: Cohesion
Definition:
A measure of how closely related and focused the responsibilities of a single module are.
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Term: Functional Cohesion
Definition:
The highest form of cohesion, where all elements contribute to a single well-defined function.
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Term: Sequential Cohesion
Definition:
A type of cohesion where the output from one part serves as input to another part, maintaining a sequence of operations.
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Term: Communicational Cohesion
Definition:
A type of cohesion where all elements operate on the same input data or produce the same output data.
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Term: Coupling
Definition:
A measure of the degree of interdependence between software modules.