An example of logical cohesion is a module that groups together functions that perform similar but ultimately unrelated operations, such as handling all I/O operations for an application within a single module.
Let's break this down:
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Cohesion in Software Design: Cohesion refers to the degree to which the elements inside a module belong together. High cohesion is generally desired, as it leads to more maintainable, understandable, and reusable code.
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Logical Cohesion Explained: Logical cohesion occurs when a module contains functions or code sections that perform logically similar operations, but are otherwise unrelated. This means the functions are grouped together because they seem related from a high-level perspective, rather than because they directly contribute to a single, well-defined purpose.
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The I/O Module Example (Expanded): Imagine a module named "IO_Operations". This module might contain functions such as:
Read_From_File()Write_To_File()Print_To_Console()Send_Network_Request()
While all these functions deal with input/output, they are fundamentally different operations. Reading from a file is quite distinct from sending a network request. The only thing they have in common is that they are I/O operations.
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Why Logical Cohesion is Problematic:
- Reduced Reusability: It becomes harder to reuse individual functions when they are tightly coupled within a module that performs diverse tasks. You might need
Read_From_File()for a specific task, but you're forced to import the entireIO_Operationsmodule, even if you don't need the other functions. - Increased Complexity: The module becomes more complex and harder to understand, as it handles multiple unrelated responsibilities.
- Maintenance Difficulties: Changes to one I/O operation (e.g., modifying the
Send_Network_Request()function) might inadvertently affect other unrelated functions in the module. - Lower Testability: It becomes harder to write focused unit tests for individual functionalities when they're bundled together in a logically cohesive module.
- Reduced Reusability: It becomes harder to reuse individual functions when they are tightly coupled within a module that performs diverse tasks. You might need
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A Better Approach (High Cohesion): A more cohesive approach would be to separate the I/O operations into distinct modules based on their purpose. For example:
File_IO_Module(containingRead_From_File()andWrite_To_File())Console_IO_Module(containingPrint_To_Console())Network_IO_Module(containingSend_Network_Request())
This promotes single responsibility principle, enhances reusability, and simplifies maintenance.
In summary, logical cohesion, while seemingly organized, can lead to increased complexity and reduced maintainability in software design. A higher degree of cohesion, where each module focuses on a single, well-defined task, is generally preferred.
