Levels of Cohesion

Levels of Cohesion

• Object Cohesion -  Occurs when a single entity is represented by the object and all operations on the object, and no others are included within it. This is the strongest type of cohesion and should be aimed by the designer.

• Functional Cohesion – Occurs when all the elements of the module combine to complete one specific function. This also strong cohesion and should be recommended.

• Sequential Cohesion – Occurs when the activities (more than one purpose  to the function) combine such that the output of one activity is the input to the next. Not as good as functional cohesion but  still acceptable.

• Communicational Cohesion – Occurs when a module performs a number of activities on the same input or output data.For example customer maintenance functions add,delete, update and query are related through communication because they all  use user customer file.

• Procedural Cohesion – Occurs when a modules internal activities bear little relationship to one another but control flows  one to another in sequence. 

• Temporal Cohesion -  Occurs when functionality is grouped simply because it occurs at the same time.  For example house keeping tasks at the start and ednd of an application. 

• Logical Cohesion – Occurs when functionality is grouped by type. For example all creates together, all updates together etc. This should be avoided at all cost.

• Coincidental Cohesion -  Occurs when functionality is grouped randomly. Not even to be considered as an option in design.