Comparison of McCall’s Quality Model with ISO 9126 Quality Model :

• McCall’s Quality Model and ISO 9126 Quality Model focus on the same abstract entity, namely, software quality, it is natural that there are many similarities between the two models.

• What is called as Quality Factor in McCall’s Model is called quality characteristic in the ISO 9126 model.

• High level quality characteristics/factors such as reliability, usability, efficiency, maintainability and portability are found in both the models.

• However, there are several differences between the two models as follows :

  1. The ISO 9126 Model emphasizes characteristics visible to the users, whereas the McCall model considers internal qualities as well. For example, reusability is an internal characteristic of a product. Product developers strive to produce reusable components, whereas its impact is not perceived by customers.

  2. In McCall’s Model one quality criterion can impact several quality factors, whereas in the ISO 9126 model, one subcharacteristic impacts exactly one quality characteristic.

  3. A high-level quality factor, such as testability, in the McCall model is a low-level subcharacteristic of maintainability in the ISO 9126 Model.

  4. McCall suggests 11 high- level quality factors whereas, the ISO 9126 standard defines only 6 quality characteristics.

  5. Some of the quality factors in McCall Model are important to developers, such as, reusability and interoperability. However, the ISO 9126 Model just considers the product.

  6. Interoperability is not an independent, top level quality characteristic in the ISO 9126 model as compared to McCall’s Quality Model.