McCall’s Quality Model

McCall’s Software Quality Model was introduced in 1977. This model is incorporated with many attributes, termed software factors, which influence software. The model distinguishes between two levels of quality attributes:

• Quality Factors
• Quality Criteria

Quality Factors: The higher-level quality attributes that can be accessed directly are called quality factors. These attributes are external. The attributes at this level are given more importance by the users and managers.

Quality Criteria: The lower or second-level quality attributes that can be accessed either subjectively or objectively are called Quality Criteria. These attributes are internal. Each quality factor has many second-level quality attributes or quality criteria.

Example: The usability quality factor is divided into operability, training, communicativeness, input/output volume, and input/output rate. This model classifies all software requirements into 11 software quality factors. The 11 factors are organized into three product quality factors: Product Operation, Product Revision, and Product Transition.

Factors of Product Quality

Below are the factors of Product Quality, that are discussed in detail.

Factors of Product Quality

Product Operation

It includes five software quality factors, which are related to the requirements that directly affect the operation of the software such as operational performance, convenience, ease of usage, and correctness. These factors help in providing a better user experience.

• Correctness: The extent to which software meets its requirements specification.
• Efficiency: The number of hardware resources and code the software, needs to perform a function.
• Integrity: The extent to which the software can control an unauthorized person from accessing the data or software.
• Reliability: The extent to which software performs its intended functions without failure.
• Usability: The extent of effort required to learn, operate, and understand the functions of the software.

Product Revision

It includes three software quality factors, which are required for testing and maintenance of the software. They provide ease of maintenance, flexibility, and testing efforts to support the software to be functional according to the needs and requirements of the user in the future.

• Maintainability: The effort required to detect and correct an error during maintenance.
• Flexibility: The effort needed to improve an operational software program.
• Testability: The effort required to verify software to ensure that it meets the specified requirements.

Product Transition

It includes three software quality factors, that allow the software to adapt to the change of environments in the new platform or technology from the previous.

• Portability: The effort required to transfer a program from one platform to another.
• Re-usability: The extent to which the program’s code can be reused in other applications.
• Interoperability: The effort required to integrate two systems.

Questions for Practice

1. Which of the following is not one of three software product aspects addressed by McCall’s software quality factors? [UGC-NET 2017]

(A) Ability to undergo change

(B) Adaptability to new environments

(C) Operational characteristics

(D) Production costs and scheduling

Solution: Correct answer is (D).

2. Which one is not a product quality factor of McCall’s quality model?

(A) Product Revision

(B) Product Operation

(C) Product Specification

(D) Product Transition

Solution: Correct Answer is (C).

FAQs

1. What is McCall’s Quality Model?

Answer:

McCall’s Quality Model classifies all software requirements into 11 different types of software quality factors.

2. What is the purpose of the Quality Model?

Answer:

The purpose of the Quality Model is to provide the basis for specifying quality requirements and evaluating quality.

4. How is Boehm’s Quality Model better than McCall’s Quality Model?

Answer:

McCall’s Quality Model focuses on only high-level characteristics whereas Boehm’s Quality Model works on a wide range of characteristics.