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TopDefinitions Of Usability
The term “usability” has evolved from a simple concept of ease of use to a construct with multiple dimensions that was adopted as part of the ISO/IEC Software engineering - Product quality model 9126. The ISO/IEC 9126 is an international standard for the evaluation of software quality. The standard was developed by The ISO (the International Organization for Standardization) and the IEC (International Electrotechnical Commission). The two organizations ISO and IEC were established by “member organizations” for the purposes of providing agreement and a level of uniformity on technical issues (ISO/IEC 9126, 1991). The fundamental objective of this standard is to address some of the well-known human biases that can adversely affect the delivery and perception of a software development project.
The 9126 standard defines six software quality characteristics that minimally overlap (Functionality, Relieability, Usability, Eficiency, Maintainability, and Portability). Together these characteristics provide a baseline for description and further refinement of software quality (ISO/IEC 9126, 1991 p 1).
The construct of Usability is often defined as a set of attributes that bear on the effort needed for use, and on the individual assessment of such use, by a stated or implied set of users. It is generally accepted to have five sub-classifications: understandability, learn ability, operability, attractiveness and usability compliance.
This user interface centric view was later expanded in ISO 9241-11 (1998) which defines usability as “the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use.” This expansion of usability into a wider system view was later adopted and renamed to “quality in use” in ISO 9126-1 (2001) (Bevan, 1999).