The majority of systems and services provided by computer science, electrical engineering and information technology are ultimately meant for human users.
If such systems and services are to be successful and usable, the focus must therefore be on the user and their behavior as part of the interaction process. Design principles for human-machine interfaces can be derived from this work and requirements defined regarding the technologies underpinning the system. Conversely, however, new opportunities for interface design, and, in turn, innovative forms of interaction, also arise from the available technologies.
The three levels of usability
Usability is defined (in ISO 9241 Section 11) as "the extent to which a product can be used by certain users in a certain usage context in order to achieve certain targets effectively, efficiently and satisfactorily." Thus the usability - or more generally the quality - of information and communication technology systems encompasses at least three levels:
- The principles of human behavior and human perception that will determine the interaction;
- The design of the interface between the user and the system; and
- The basic technologies on which an interaction is based.
At each level, different media and modalities and combinations thereof can be considered; when it comes to actual use, the most relevant is the auditory, visual and tactile interaction. Interaction covers both interactions between people and machines (e.g., voice-based interfaces, Web interfaces, interactions with avatars and in virtual environments) and between people via a technical system (voice and multimedia services via wired or wireless networks, translation systems, etc.).
Measuring quality and usability
In order to optimize the design of these systems, consistent measuring techniques must be used to record and analyze their quality and usability. Usability is therefore seen as the product of a measuring and prediction task in which the properties of the system are correlated with the requirements of the user.
Auditory or visual experiments
To this end the performance of the system and its components must be quantitatively measured. But the perceptions and requirements of the user must also be quantified in interaction with the system. The latter can be done, for example, through auditory or visual experiments with human test subjects in which the properties of the test systems are set in a controlled way and the judgments and behavior of the user are recorded.
Predicting usability
The system properties can be harmonized with the perceptions of the user and design principles can be derived for the systems. Ideally, the quality and usability of a system can be predicted while it is still in planning and development. The models needed for this must be able to quantify quality to the same level of validity and reliability as the judgment of a human user of the system (as a direct quality value).
That is how to make technology successful
By a combination of measuring and predicting quality and usability, systems and transmission networks can be adapted in a targeted, economical way to the requirements of the user and thus substantially increase acceptance and the success of technical systems.