Utilisability

The utilisability or usability is defined by the standard ISO 9241 as “the degree according to which a product can be used, by identified users, to reach definite goals with Efficacité, Efficience and Satisfaction, in a context of use specified”.

It is a concept close to that of Ergonomie, which is however broader.

The Critère S of the utilisability are:

effectiveness: the product makes it possible its users to reach the result envisaged;
efficiency: reached the result with a less effort or requires a minimal time;
satisfaction: Comfort and subjective evaluation of the Interaction for the user.

Utilisability and ergonomics

One can compare this definition with that proposed in 2000 by the IEA (International Ergonomics Association) “ergonomics (or Human Factors ) is the scientific discipline which aim at the fundamental comprehension of the interactions between the human ones and the other components of a system, and the profession which applies theoretical principles, data and methods in order to optimize the wellbeing of the people and the total performance of the systems”. One finds here the concepts of performance and wellbeing. Although implicit one can consider that the concept of efficiency forever be does not go away that it is through the concepts of Workload or through the permanent concern of industrial ergonomics to make coincide its proposals for an improvement of the situations of work with the maintenance or the improvement of the Productivité.

The principal difference lies in the origin of these concepts. Whereas ergonomics is mainly resulting from a concern of improvement of the Work conditions, the utilisability is closer to the steps quality. These two currents can meet, insofar as a software usable is potentially a better tool if it must be used in a situation of work. One can however raise the absence of the health-safety of the explicit concerns of the utilisability. Another difference lies in the fact that the literature on the utilisability particularly does not seem by making distinction between work and not-work and applies readily the same methods to all kinds of “directed activities” ( purposeful activities ) that it is of an online shopping or an Intranet, a game console or a system of telephony in company.

Utilisability and utility

Nielsen (1994) locates the concept of utilisability within a broader concept of acceptability of a system. It describes this model by a tree where the acceptability of a system divides of practical and social acceptability. Practical acceptability includes in its turn a certain number of characteristics of which reliability and performances and the utility ( usefulness ). Following Grudin (1992), Nielsen divides then this utility into utility and usability (utilisability). This model highlights the importance of the utilisability for acceptance (and thus success) of a system while stressing that it is only one component of this acceptability. Another important aspect is the distinction between utility and usability . In other words, does the ergonomicist have to be concerned with know if the system with the development of which it participle is used for something or must it be simply satisfied to optimize this system without worrying about the relevance with the goals suggested?

A system can respect all the criteria of utilisability but be useless. It is the adequacy between the activity and the tool which will make it possible to say that this tool is useful.

The methods of analysis of the activity enable us to encircle which functionalities must provide the application, in other words which functionalities are useful. An ergonomic system of good quality will have to be at the same time useful and usable.

Characteristics of a system usable

Nielsen also breaks up the concept of utilisability into five major characteristics of a system usable. Efficiency ( efficient to uses ) and satisfaction ( subjective satisfaction ) are found such which in the standard ISO 9241. The Facilitated training ( easy to learn ), the facility of appropriation ( easy to remember ) and the reliability ( few errors ) can be regarded as components of the effectiveness. According to Nielsen (1994) and Mayhew (1999), a step of improvement of the utilisability must decide which of these criteria are more important. In particular, the facility of training and efficiency can be contradictory objectives. It is thus advisable to know if the developed tool is addressed rather to users beginners and specific or with expert.

This problem joined another aspect of the definition recalled to the beginning of this article, insistence on the existence of “identified users”, “definite goals” and a “context of use specified”. The world of the utilisability is only taking the full measurement of the importance of this context of use by the means of methods like the Contextual design, or of the interest for the Ethnologie, the Cognition located and distributed and the Théorie of the activity. One can bring this evolution closer to the distinction made by of Montmollin between an ergonomics of the human factor and an ergonomics of the activity, the utilisability incorporating elements of the second gradually.

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