Quality and Usability

What is usability?

The majority of systems and services provided by computer science, electrical engineering and information technology are ultimately aimed at a human user. For the success of such systems and services, it is therefore essential to address the user and his or her behavior during interaction.

From this, design principles for human-machine interfaces can be derived and requirements for the technologies underlying the system can be defined. Conversely, the available technologies also give rise to new possibilities for interface design, and from these new forms of interaction.

The three levels of usability

The English term "usability" is usually translated into German as "Gebrauchstauglichkeit". It is defined according to ISO 9241 Part 11 as "the extent to which a product can be used by specific users in a specific context of use to achieve specific goals effectively, efficiently, and satisfactorily". The usability discipline, which is assigned to the Faculty of Electrical Engineering and Computer Science, therefore captures the usability - or more generally the quality - of information and communication technology systems on at least three levels:

  • The level of the principles of human behavior and human perception that will determine the interaction;
  • the level of the design of the interface between user and system; and
  • The level of the enabling technologies that underlie interaction.

At each of the levels, different media or modalities and combinations of them can be considered; the most relevant for application here are auditory, visual, and tactile interaction. Interaction includes both that between humans and machines (e.g., voice-based interfaces, web interfaces, interactions with avatars and in virtual environments) and an interpersonal interaction via a technical system (voice and multimedia services via wired or wireless networks, translation systems, etc.).

Measurement of "Quality" and "Usability

For the optimal design of the aforementioned systems, their quality and usability must be consistently measured and analyzed. Usability is therefore understood as the result of a measurement and prediction task in which the properties of the system are related to the requirements of the user. For this purpose, on the one hand, the performance of the system and its components must be recorded quantitatively. On the other hand, the user's perceptions and requirements in interaction with the system must also be quantified. The latter can be accomplished e.g. by auditory or visual experiments with human test persons, in which the properties of the considered systems are adjusted in a controlled way and the judgments as well as the behavior of the user are recorded.

The system properties can be correlated with the user's perceptions, and design principles for the systems can be derived. Ideally, the quality and usability of a system can be predicted during planning and development. The models required for this must be able to quantify quality validly and reliably in a way that corresponds to the judgment of a human user of the system (as a direct measure of quality). By combining the measurement and prediction of quality and usability, systems and transmission networks can be adapted to user requirements in a targeted and economical manner, thus considerably increasing the acceptance and success of technical systems.


Therefore, the long-term goal of the usability research group is to

  • to develop measurement methods for the quality and usability of information and communication technology systems,
  • to relate these to system properties,
  • to derive requirements for the system design,
  • to predict quality and usability on the basis of system properties, and
  • apply the described procedures in the usability cycle of specification, planning, design, implementation, optimization and monitoring.




The systems and services considered here include, for example, those

  • for the transmission of voice, audio and video signals (telephony, voice-over-IP, broadcasting, IP-based television, teleconferencing, etc.),
  • for multimodal human-machine interaction (voice dialog systems, web-based services, multimodal dialog systems, etc.),

as well as, in a broader sense, to multimodal interaction between humans, machines, and the environment (virtual environments, augmented environments, context-sensitive systems, etc.).

Study at the "QU Lab"

For students of electrical engineering and (technical) computer science, the topic and the approach described offer the advantage that they can assess the effects of the systems they develop on the user, and that they are excellently prepared for interdisciplinary work. Therefore, courses on the described topics are offered within the department that address all three levels - technology, interaction design, and user.