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Introduction
Complex computer systems are finding their way into everyday life, and at the same time the market is becoming saturated with competing brands. This has led to usability becoming more popular and widely recognised in recent years as companies see the benefits of researching and developing their products with user-oriented instead of technology-oriented methods. By understanding and researching the interaction between product and user, the usability expert can also provide insight that is unattainable by traditional company-oriented market research. For example, after observing and interviewing users, the usability expert may identify needed functionality or design flaws that were not anticipated. In the user-centered design paradigm, the product is designed with its intended users in mind at all times. In the user-driven or participatory design paradigm, some of the users become actual or de facto members of the design team. The term user friendly is often used as a synonym for usable, though it may also refer to accessibility. The use of terms user friendly and user friendliness should be avoided, as there are no widely accepted definitions for them, and they are thus often used without much substance.
Defining usabilityUsability is often associated with the functionalities of the product (cf. ISO definition, below), in addition to being solely a characteristic of the user interface (cf. framework of system acceptability, also below, which separates usefulness into utility and usability). For example, an automobile lacking a reverse gear could be considered unusable according to the former view, and lacking in utility according to the latter view. When evaluating user interfaces for usability, the definition can be as simple as "the perception of a target user of the effectiveness (fit for purpose) and efficiency (work or time required to use) of the Interface". Each component may be measured subjectively against criteria e.g. Principles of User Interface Design, to provide a metric, often expressed as a percentage. It is important to distinguish between usability testing and usability engineering. Usability testing is the measurement of ease of use of a product or piece of software. In contrast, usability engineering (UE) is the research and design process that ensures a product with good usability. Usability is an example of a non-functional requirement. As with other non-functional requirements, usability cannot be directly measured but must be quantified by means of indirect measures or attributes such as, for example, the number of reported problems with ease-of-use of a system. ISO standardThe document ISO 9126 (1991) Software Engineering Product Quality, issued by the International Organization for Standardization, defines usability as:
The document ISO 9241-11 (1998) Guidance on Usability, also issued by the International Organization for Standardization, defines usability as:
System acceptabilityUsability consultant Jakob Nielsen and computer science professor Ben Shneiderman have written (separately) about a framework of system acceptability, where usability is a part of "usefulness" and is composed of:
Usability considerationsUsability includes considerations such as:
Other considerations
Examples of ways to find answers to these and other questions are: user-focused requirements analysis, building user profiles, and usability testing. ConclusionUsability is now recognized as an important software quality attribute, earning its place among more traditional attributes such as performance and robustness. Indeed, various academic programs focus on usability. [1] Also several usability consultancy companies have emerged, and traditional consultancy and design firms are offering similar services. See also
References
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