Exploring Layering in Software: A Module Arrangement Guide

What is LAYERING ARRANGEMENT OF MODULES | What is Layering in Software engineering ?

• In a layered design solution, the modules are arranged into layers based on their call realationship.
• A module is allowed to call only the modules that are at a lower layer , i.e, a module should not call al module that is either at higher layer or even in the same layer .

Technologies of Layered Design :-

• Super-ordinate :-   A module that controls another module.

• Sub-ordinate :-      A module which is controlled by another module .

• Visibility :-             A module  'A'  is said to be visible to another module 'B' , i 'A' directly or indirectly calls 'B'.

GOOD CONTROL ABSRACTION

POOR CONTROL ABSTRACTION

• Control Abstraction :- The modules at higher layers should not be visible to the layers of lower layer .

• Depth and Width :- Number of leves of controls and span of control.

      In this above example Depth=3 , Width=3

• Fan-out :- The number of modules that are directly controlled by a given module . 

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