McCall's Software Quality Model

Yatharth AggarwalMayank Chauhan

IV.4 Software Engineering

Quality can be defined as.....

• Conformance to requirements

• Fitness for the purpose

• Level of satisfaction

Introduction…

• Jim McCall (McCall, Richards & Walters, 1977) introduced this model (also known as theGeneral Electrics Model of 1977).

• This model, as well as other contemporary models, originates from the US military (itwas developed for the US Air Force, promoted within DoD) and is primarily aimedtowards the system developers and the system development process.

• This quality model attempts to bridge the gap between users and developers by focusingon a number of software quality factor that reflect both

users’ views

developers’ priorities.

• At NASA, the criteria for evaluation of software quality are taken from McCall’s softwarequality factor model.

The model

Product Operation

Product revision

Product transition

identifies quality factors that influence the extent to which the software fulfils its specification

Quality factors (representation of behavioral characteristic of a system)

• Product Operation

Correctness : Does it do what customer wants ? (meeting specifications)

Efficiency : Does it quickly solve the intended problem ? (enough computing resources)

Integrity : Is it secure ? (access limitations to people)

Reliability : Does it do it accurately all of the time ? (successful performance)

Usability : Can I run it ? (efforts in learning/operating)

Quality factors (dependence of a system on ethical issues)

• Product Revision

Maintainability : Can it be fixed ? (fixing bugs and errors)

Flexibility : Can it be changed ? (modifying an operational program)

Testability : Can it be tested ? (ensuring performance)

• Product Transition

Portability : Can it be used on another machine ? (platform dependence)

Reusability : Can parts of it be reused ? (generic coding)

Interoperability : Can it interface with other system ? (coupling system)

Quality criteria (attribute of a quality factor related to software development)

Quality criteria (subject validating the factors of quality mgmt.)

Quality criteria (many-many relation b/w factors and criteria)

Relationship Between Quality Factors and Quality Criteria

• Each quality factor is positively influenced by a set of quality criteria, and the same quality criterion impacts a number of quality factors.

• Example: Simplicity impacts reliability, usability, and testability.

• If an effort is made to improve one quality factor, another quality factor may be degraded.

• Portable code may be less efficient.

• Some quality factors positively impact others.

• An effort to improve the correctness of a system will increase its reliability.

Thank you …………………

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