Cohesion in context with component level design refers that a component or class encapsulates only attributes and operations that are closely related to each other and to the class or component itself.
TYPES OF COHESION
Functional
It is exhibited mainly by operations. This type of cohesion occurs when a module performs one and only one computation and then returns a result.
Layer
It is exhibited by packages, components, and classes. This type of cohesion occurs when a higher layer accesses the services of a lower layer, but lower layers do not access higher layers.
Temporal
Operations that are performed to reflect a specific behavior or state.
Procedural
Components and operations are grouped together. It allows one to be invoked immediately after preceding one was invoked. It is done even if there is no data is passed between them.
Communicational
Operation on same data are defined in one class. Classes and components that exhibit functional, layer, and communicational cohesion are easy to implement, test and maintain.
Sequential
Components and operations are grouped in such a manner that the first one provides input to the second one and so on.
Utility
Components, classes, or operations exist in the same category but are otherwise unrelated are grouped together. This type is less used.
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