Sequential cohesion is one of the levels of cohesion in software engineering that describes how closely the tasks or operations within a module or component are related to one another in terms of sequence or order of execution. Modules with sequential cohesion are designed so that the tasks are performed in a specific, predetermined sequence. This means that each task relies on the output of the previous one, and there is a strict, linear flow of control within the module. While sequential cohesion is not as desirable as functional cohesion (where tasks are related by a common function), it can be appropriate in certain situations. Here are key characteristics and considerations related to sequential cohesion:
Linear Flow: Modules with sequential cohesion have a linear flow of control, where one task follows another in a specific order. The output of one task serves as the input for the next.
Specific Sequence: The sequence of tasks within a module is typically predetermined and rigid. Deviating from this sequence may result in errors or unexpected behavior.
Limited Independence: Tasks within a module with sequential cohesion are less independent of each other compared to functionally cohesive modules. Changing one task may require adjustments in subsequent tasks.
Reduced Reusability: Modules with sequential cohesion are often less reusable because they are tightly coupled to the specific sequence of tasks. Reusing such a module in a different context may not be straightforward.
Maintenance Challenges: Sequentially cohesive modules can be more challenging to maintain, especially when updates or changes are required. A modification in one task may necessitate reviewing and modifying subsequent tasks.
Examples: Examples of modules with sequential cohesion might include a module that processes a series of data records one at a time in a specific order, or a module that guides a user through a series of steps in a wizard-like interface.
Situational Applicability: Sequential cohesion may be suitable in situations where a strict order of operations is necessary, and the module's primary purpose is to manage and control that order. For example, in a state machine or a control flow module.
Balancing Cohesion and Coupling: When designing software, it's important to balance cohesion and coupling. While sequential cohesion may be appropriate for certain tasks, it's generally desirable to aim for higher levels of cohesion, such as functional cohesion, within modules to promote modularity and maintainability.
In summary, sequential cohesion is a level of cohesion in software engineering that describes modules where tasks are closely related by a specific sequence or order of execution. While not as flexible or modular as functionally cohesive modules, sequentially cohesive modules can be useful in situations where strict control over the sequence of operations is required. However, careful consideration should be given to the potential maintenance and reusability challenges associated with such modules.
