How important is Design Quality in our Software Industry and what are the Metrics used for the same?

CMMI FAQ 0

12th May, 2014

Designing is one of the most important activity for the SDLC and at the same time the least-focused or talked-about activity. Most of the developers are not keen to document the requirements & design of their project and that leads to many issues later on in subsequent phase of SDLC. It also has many side effects like delay in delivery (schedule variance), effort variance, cost variance, more review effort, more defects etc.

Design activity starts when baseline requirements are available. Design serves as the blueprint for the project and laid down the basis for project plan.

What is Design Quality?

There are many different criteria for judging a Design quality including simplicity, efficiency, modularity, abstraction, coupling & cohesion etc.

What are different Metrics measured for Design Quality?

Following are some of the measurement (metrics) that are used to measure the design quality:

1. Network Metrics: These metrics focus on the structure charts and tells us about the structure of the system. The more the structure chart graph deviates from a tree, the more complex the system.
2. Stability Metrics: Stability metrics of a design helps in quantifying the resistance of a design to the potential ripple effect that is caused by changes in modules. Higher the stability betters the maintainability of program.
3. Information Flow Metric: This metric defines the complexity in terms of total information flowing (in and out) through a module.
4. Weighted Methods per Class (WMC): This defines the effort in developing a class and is determined by the number of methods in the class and their complexity.
5. Number of Children (NOC): This metric defines the number of children in terms of immediate subclasses of a class.
6. Coupling between classes (CBC): CBC value of a class is the total number of other classes to which the class is coupled. Two classes are said to be coupled together if methods of one class use methods or instance variables of other class.

As a developer or project manager you can consider metrics listed above to improve the design quality.

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Rajendra Khare (MD)
DQS Certification India Private Limited
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