The system utility

Utility

In economics, utility is a measure of customer satisfaction, referring to the total satisfaction received by a consumer from consuming a good or service....

may be defined in terms of the satisfaction of the system stakeholders.

Actual Utility

The actual utility (or usefulness) is the actual stakeholders' satisfaction.
The actual utility may be measured using customer satisfaction

Customer satisfaction

Customer satisfaction, a term frequently used in marketing, is a measure of how products and services supplied by a company meet or surpass customer expectation...

 questionnaires.

The utility life cycle

Life cycle

Life cycle or lifecycle may refer to: * Biological life cycle* Enterprise life cycle* Life cycle assessment* New product development* Product lifecycle , various meanings* Project life cycle...

 

The value of the actual utility is not static. It changes in time, according to the system maturity

Maturity

Maturity may refer to:*Sexual maturity, the stage when an organism can reproduce, though it is distinct from adulthood*Mature technology, a term indicating that a technology has been in use and development for long enough that most of its initial problems have been overcome*Maturity , a geological...

.

The utility function has two phases: The startup and the main phase.

• The startup phase begins with the initial usage of the system and ends with the utility function reaching maximum utility.

The initial value of the utility function is determined by the intuitivity of the user interface.
The slope from the initial value to the maximum value is determined by the learnability

Learnability

-Software testing:In software testing learnability, according to ISO/IEC 9126, is the capability of a software product to enable the user to learn how to use it...

.

• Following the startup phase is the beginning of the main phase, in which the utility function stabilizes. Then the system utility gradually decreases. The reasons for the utility decrease include hardware reliability and maintenance costs, well know in common QA
  QA
  QA may stand for:* Qatar, ISO 3166-1 alpha-2 country code** .qa, the country code top level domain for Qatar* Quality assurance, the process or set of processes used to measure and assure the quality of a product...
  
  . Additional reasons for the decrease in the system utility may be attributed to human factors
  Human factors
  Human factors science or human factors technologies is a multidisciplinary field incorporating contributions from psychology, engineering, industrial design, statistics, operations research and anthropometry...
  
  , such as use error
  Use error
  The term Use Error has recently been introduced to replace the commonly-used terms human error and user error. The new term, which has already been adopted by international standards for medical devices, suggests that accidents should be attributed to the circumstances, rather than to the human...
  
  s and the user’s capability to handle system faults.

The utility function may be described as in the following chart: