1. On the Criteria To Be Used in Decomposing Systems into Modules
D.L. Parnas Carnegie-Mellon University

2. MODULARIZATION What is modularization ?
Decomposing a system into smaller independent segments that have their own well defined inputs and outputs. These segments are generally called as Modules and the process of this segmentation is called Modularization.
Why is it required ?
Managerial
Product flexibility
Comprehension

3. CRITERIA Based on every major step in the program
Flowchart
Suitable for small systems
Based on Information hiding
Design decisions
Hides knowledge from others
Independent from each other

4. SPECIFIC CRITERIAS Few examples of specific modules that are advisable
Data structures, its access and modifying procedures
The call to a routine and the routine itself
Formats of control blocks
Character codes, alphabetic orderings and similar data
The sequence in which certain items will be processed
Note: Decomposition is not the same as hierarchical structure.

5. CONCLUSION
The criteria for decomposing a program must be based on information hiding and design decisions rather than flow of procedure and major actions.
This enables the programmers to change the functionality of the program by changing the respective module and not rewriting parts of modules that rely on that functionality.
The processes of integration, testing and maintainability are simplified

6. Discussion Do you agree with the author ?
Any other criteria for decomposition ?
Importance of hierarchy while decomposing
Examples of bad decomposition