Cohesion and Coupling are two very important terms in the field of software engineering. Both Cohesion and Coupling play important roles in different parts of software design.
Cohesion in software refers to how the elements in a component or module work together. It is also called ‘Intra-Module Binding.’ Engineers aim to have high cohesion. High cohesion means the elements work better together and are focused. Lower cohesion in software development makes elements perform unrelated or unwanted tasks.
Coupling in software engineering mainly focuses on the relationship between modules. Coupling is also called ‘Inter-Module Binding. A higher Coupling between modules makes modules more dependent on each other. Software engineers aim to avoid high coupling as it makes modules more complicated. Lower Coupling helps modules be easier to work with and more flexible.
Common Coupling, External Coupling, Stamp Coupling, Data Coupling, Content Coupling, Control Coupling, No-Data Coupling
Importance of Modules in Software Engineering
Before diving into Cohesion and Coupling in software engineering, it is important to understand what role modules play in software. Modules play a key-role in making complicated systems simple in software engineering.
Modularization is the process in which parts of a software system are broken into several different parts that are called ‘modules’. Each module is assigned a different task which it has to complete. This division helps simplify technical software.
Listed below are some advantages of modules in software engineering:
Easy to Understand: With the division of software into modules, it makes understanding systems a lot easier for engineers.
Maintenance: Software that is broken into modules is significantly easier to maintain. Problems and bugs can be found and addressed in specific modules without having to make a lot of changes to the overall system.
Convenience: With every module having a specific task, it is easier for developers to work on and improve the ways modules work towards their goals.
Cohesion and Coupling in software engineering help improve the efficiency and the overall functioning of modules in software.
Cohesion in software engineering in simple terms, means the relationship between components within a system. It mainly refers to the degree to which the elements in a component or module work to complete a task. Cohesion helps determine which elements within components are related to each other.
Software engineers aim to have high Cohesion in their software. Systems with higher rates of cohesion help perform tasks much better and more efficiently. Lower cohesion between elements in components makes it difficult for elements to complete required tasks. A higher cohesion rate helps systems have better functioning and maintainable software.
Provided below are the main types of Cohesion in software engineering.
Types of Cohesion in Software Engineering
The types of Cohesion in software engineering are as follows:
Cohesion Type
Details
Functional Cohesion
This type of Cohesion occurs when all elements are related to one properly defined function. The models part of functional cohesion work together to complete tasks. This type of Cohesion only works to complete assigned tasks at hand.
Logical Cohesion
Logical Cohesion exists in a model when all functions have been assigned to a single task. Elements within Logical Cohesion are grouped together because they do logically similar tasks. Modules with high Logical Cohesion are difficult to maintain.
Communication Cohesion
Communicational Cohesion in a module occurs when elements operate with the same data. These elements usually are related by their data inputs and outputs.
Coincidental Cohesion
In Coincidental Cohesion, Elements in modules are almost completely unrelated. There is barely any cohesion. This is considered to be the worst form of Cohesion between elements in a module.
Temporal Cohesion
Elements within Temporal Cohesion are related by their time of executing tasks. Temporal Cohesion allows multiple tasks to be executed at the same time within a module.
Procedural Cohesion
Elements within Procedural Cohesion are organized into a specific series of steps in a module to achieve and complete tasks,
Sequential Cohesion
In Sequential Cohesion, an output from one element is taken as the element of another. This helps in the efficient grouping of elements within a module. This type of Cohesion is easier to maintain. Tasks are easier to complete as they are in a simple and logical sequence.
Coupling in simple terms, means modules are related to each other. Coupling measures how dependent elements are on others and whether they can function on their own. Software engineers aim to have low Coupling within their software.
High coupling in modules is often not desired. Lower coupling means modules can function properly on their own and are more flexible. They also ensure quicker and more focused completion of tasks. Lower coupling also makes modules more easy to maintain by developers.
Types of Coupling in Software Engineering
There are different types of coupling in software engineering. Each type has its functions and designated purpose. Provided in the table below are some of the types of coupling in software engineering.
The different types of Coupling in software engineering are listed as follows:
Coupling Type
Details
Common Coupling
When two modules share the same type of global data with each other, it is referred to as Common Coupling. Any changes to the global data or data of one module affect the data of the related modules as well.
External Coupling
This type of coupling forms when 2 or more modules rely on an external source to function. These external sources include databases or APIs. These modules can change independently.
Stamp Coupling
Stamp Coupling is when modules share a similar data structure. However, only some parts of the data structure of one module are relevant to the other.
Data Coupling
In Data Coupling, only a specified form of data is relevant and shared between modules. This is often considered to be a highly desired form of Coupling as it is efficient. It reduces unnecessary dependencies between modules as well.
Content Coupling
Content Coupling results in the complete flow of data from one module to another. This results in one module being completely dependent on another. This is a highly unwanted form of Coupling in software engineering. This is considered to be the worst form of Coupling.
Control Coupling
The data of one module affects the execution of tasks of another module in Control Coupling. Essentially, one module can control the behavior of another. This is another unwanted form of Coupling in software engineering and is considered poor design.
No-Data Coupling
No-Data Coupling refers to when modules don’t share any data with each other. This form of Coupling is often the most desired as modules are not dependent on each other. This allows each individual module to solely focus on their required task. No-Data Coupling allows modules to be fully independent and reusable.
Main Differences between Cohesion and Coupling in Software Engineering
Cohesion and Coupling are very important parts of software systems. Both have different purposes, tasks and roles to play. Listed below are the differences between Cohesion and Coupling in Software Engineering.
The differences between Cohesion and Coupling in Software Engineering is as follows:
Cohesion
Coupling
Cohesion is referred to as Intra-Module Binding. It is mainly concerned with the relationship of the elements in modules.
Coupling is referred to as Inter-Module Binding. It is concerned with the relationship between modules.
Cohesion mainly requires elements in one particular module to work together to complete a task.
Coupling mainly deals with the independence or interdependence of different modules with each other.
A high amount of Cohesion is considered good in software engineering. High cohesion means that the more elements can work together better to achieve tasks.
A high amount of Coupling is unwanted in software engineering. This means modules are more dependent on each other.
A low amount of Cohesion is not good in software engineering. A low amount of Cohesion makes it harder to complete certain tasks.
A low amount of Coupling is considered good in software engineering. This means that modules can be flexible and independent.
Good software requires high Cohesion.
Good software requires low Coupling.
High Cohesion makes software easier to manage and maintain.
Low Coupling helps modules to tasks with more flexibility. Low Coupling is desired to help with maintaining systems.
Cohesion and Coupling in Software Engineering Advantages
Provided below is an overview of the advantages of the different types of Cohesion and Coupling in software Engineering. The advantages are as follows:
Advantages of High Cohesion
The Advantages of High Cohesion in software engineering is as follows:
Advantage
Details
Reusable
Modules can be reused in different situations if required. High Cohesion also allows for modules to be used without changing them.
Maintenance
High Cohesion allows for modules to be easier to maintain.
Reduce Complexity
Modules with higher Cohesion are easier to work with as elements are not performing unrelated tasks.
Advantages of Low Coupling
Listed below are some of the advantages of Low Coupling in software engineering is as follows:
Disadvantage
Details
Flexibility
Modules with low Cohesion are able to work a lot more independently. This allows better adapting to new systems.
Maintenance
Modules with low Cohesion are easier for engineers to maintain as one module has little effect on the others.
Reusability
Modules can be used again without making many changes when having low Coupling.
Precision
Modules with low Coupling are a lot more precise and effective.
Cohesion and Coupling in Software Engineering Disadvantages
Provided below is an overview of the disadvantages when software has low Cohesion and high Coupling. The disadvantages are as follows:
Disadvantages of Low Cohesion
The disadvantages of having Low Cohesion in software engineering are as follows:
Disadvantages
Details
Maintenance
Due to its disconnected nature, modules with lower Cohesion between elements are much more difficult to maintain by engineers.
Difficult to Test
Modules with low Cohesion perform a lot of unrelated tasks. This makes software more difficult to work with and test.
Less Reusability
With lower Cohesion, the complexity of modules goes up noticeably. This makes it harder to resume without constantly making changes.
Disadvantages of High Coupling
Listed below are some of the disadvantages of High Coupling in Software Engineering:
Disadvantages
Details
Maintenance
Modules with high Coupling are significantly more difficult to maintain. This is mainly due to the fact that one module may have an effect on another.
Hard to Modify
Modules with higher Coupling are significantly harder to modify. A change or modification to one may have unintended changes on another module as well.
Less Reusability
Modules that are dependent on each other are difficult to reuse. Adjustments need to be constantly made to be able to properly reuse software with high Coupling.
Frequently Asked Questions
What are the 7 types of Cohesion?
The 7 types of Cohesion in Software Engineering are Functional Cohesion, Logical Cohesion, Communication Cohesion, Coincidental Cohesion, Temporal Cohesion, Procedural Cohesion and Sequential Cohesion.
What is the difference between Coupling and Cohesion?
In software engineering, there are a few differences between Cohesion and Coupling. The main difference however is that Cohesion refers to the relationship between elements in a module. On the other hand, Coupling refers to the relationship different modules have with each other.
What are the levels of Coupling?
There are several different types of Coupling in software engineering. Some of the types of Cohesion include Common Coupling, External Coupling, Stamp Coupling and Data Coupling.
What is Coupling in Software?
Coupling in software engineering refers to the relationship between Modules in software. Coupling helps determine the level of independence that modules have. Modules with lower Couplings are wanted by software engineers as they are easier to work on.
What is Modularity?
Modularity mainly in software engineering refers to the breaking up of a complex system into smaller components or modules. This is important to help simplify systems. These modules are assigned different roles and have to complete different tasks. Software engineers desire more independent modules.
What is Cohesion in Software?
Cohesion in software engineering refers to the relationship that elements have within a module. Software engineers want higher Cohesion between elements in modules. Modules with high Cohesion are more focused and efficient with finishing tasks.
What are the advantages of Low Coupling in Software Engineering?
Some advantages of Low Coupling in software engineering include software modules being easier to maintain, more reusable and significantly easier to work on.
