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descrizione usabilità (usability description)




 descrizione usabilità

Usabilità in Italiano

Usability is one of the eight software quality factors (according to the ISO/IEC standard 25010: 2011), along with functionality, reliability, portability, maintainability, efficiency, compatibility and security. Using a metaphor, we can say that usability, along with functionality, may be considered one of the two pillars supporting the other quality factors. The term "usability" relates to how easy it is to understand, use and also get pleasure out of using the tool. The world of information technology defines as usable a software product suited to the user's needs and expectations, intuitively operated, easy to learn, and aesthetically pleasing (principles established by Jakob Nielsen).

According to the ISO, usability-related aspects are as follows:
- recognizability: the user can recognize whether a product or system is appropriate for its need;
- learnability: the product or system can be used to achieve specific goals of learning;
- operability: the product or system has attributes that make it easy to operate and control;
- user protection: a system protects users against making errors;
- user interface aesthetics: the product enables pleasing and satisfying interaction for the user;
- accessibility: a product or system can be used by people with the widest range of characteristics and capabilities.

Interest in usability began in the 1980s, as GUIs (Graphical User Interfaces) increased their potential for expression and communication. In the past, the earliest means of human/computer communication included punched cards read by a special hardware, and hard-copy printouts, with slow,interaction. At present, the graphic interface is the quickest and most effective means of communication between people and computers - or better, between people through computers. Technological development facilitates the production of usable objects. Usability is therefore an evolutionary concept and is achieved in proportion to the producer's intuitions and technological skills. Another reason that the interface has to be user-friendly is because it is often the only part of the system with which the user enters into contact.

On the other hand, in the case of access to the system by the disabled (e.g. those with motor, visual, and hearing disabilities), our attention focuses on "accessibility" which complies with WAI regulations (see one of the presented links). Accessibility is a prerequisite for, and does not replace, usability. Removal of the entry barriers alone does not guarantee the system's ease of use or user-friendliness, although the two concepts do complement one another.

Other information about the Italian Law concerning accessibility and disabled people "Provisions to support the access to information technologies for the disabled" (Law n. 4, January 9, 2004) can be found at the address www.pubbliaccesso.gov.it where there are documents in English.

The spread of the Internet and the growing use of websites require an even greater knowledge of the techniques and methods that facilitate access to the system and use of the software. Methods oriented towards simplicity of use are given the name "usability" (or the "human factor" and "software ergonomics") and are derived from a set of studies and activities carried out in recent years, in synergy between information technology experts and psychologist.

Effective communication in a usable interface is achieved through the use of metaphors - graphic representations of common objects in lieu of verbal descriptions of the information. Effectiveness is achieved by placing the user at the centre of the design. In the 1980s, Norman defined the "user centred design" - still a model of reference for usability today. Usability assessment is a specific activity dealt with by new professions.

The user is decisively taking on central importance in the world of information technology. The traditional distinctions of hardware and software appear insufficient to describe the problems related to using computers, and have led me to adopt the new term " userware." The inherent problems - interaction, the interfaces, use, and quality in the use of software - may be grouped under this term. On the other hand, I would limit "peopleware" (De Marco, Lister, Costantine) to problems of a more general organizational, historical, economic, non-technological, knowedge-related and project-management-related nature, with regard to people working with information technologies.

At present, the new ISO/IEC standard 9126, currently being published, has differentiated the concept of quality and of the corresponding metrics into internal, external, and quality in use. This inherits, as regards usability, indications from the ISO standard 9241 "Ergonomic requirements for office work with visual display terminals" part 11 (Guidance on usability) of 1997. This standard describes aspects of interest to evaluate usability and to measure it in terms of effectiveness, efficiency, and use satisfaction. The conception of usability in 9241 is broader than what appeared in 9126 of 1991, and is a premise for the concept of quality in use in the new 9126 of 2000. In fact, the quality of the system in use is considered to incorporate mainly functionality, reliability, and efficiency.

ISO/IEC 12207 (1995) regards the activities related to the software's entire life cycle. Development, maintenance, and validation are the most important processes described regarding usability.
The development process also specifies the user interface and ergonomic aspects during the requirement analysis activity, as well as cost, functionality, security and other prerequisites. During the maintenance process, the maintainer will analyze the impact on the existing system, taking into account the type of maintenance: corrective, enhancement, preventive or adjustment. The validation support process will enable the typical user to use the software product easely and to carry out the assigned tasks. Lastly, the improvement organizational process contains some general guidelines regarding all the processes, with special focus on measurement activity and the collection of the quality costs.

An approach for interactive systems development focusing specifically on the goal of producing usable systems is described in ISO standard 13407 "Human-centred design processes for interaction systems" of 1999. In addition this approach calls for a multi-disciplinary contribution, during the design phases, of various professional skills, including ergonomics and human factor experts.

For the content of the web (data and information) also the standard ISO/IEC 25012 should be considered.

There are a number of methods to evaluate usability: some, like heuristic evaluation, are expert-based, and others, like "cooperative evaluation" and laboratory tests are user based, while special evaluations are based on questionnaires. When dealing with designers and users, the approach used must be collaborative and participatory (participatory design), as the product being developed may still be adequately modified. Even in the case of third-party auditing, it should be kept in mind that the basic players remain the designer and the domain expert user. All considerations should be made in line with the users needs, as shown at the time the test is carried out. Any consideration about usability should be constantly shared, by designers, users, and "observers," bearing in mind the final user's needs. Of course, the functionality requirements should already be agreed upon (and not open to discussion) when evaluating usability. In fact, it is believed that functionality analysis tests, which may be performed even without users, must precede the usability tests and may respond to different criteria of guidance, control, and evaluation. However, in this case as well "design review" techniques shared by the various players, may help to build the "best product proposal" to be submitted to the user in the usability test.

Other information is contained in some of the books indicated in the orientation section, and in particular in a book on quality that offers a more general picture of the qualitative and metric factors, including usability.


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