Although software engineers extensively use a component-based software engineering (CBSE) approach, existing usability questionnaires only support a holistic evaluation approach, which focuses on the usability of the system as a whole. Therefore, this paper discusses a component-specific questionnaire for measuring the perceived ease-of-use of individual interaction components. A theoretical framework is presented for this compositional evaluation approach, which builds on Taylor's layered protocol theory. The application and validity of the component-specific measure is evaluated by re-examining the results of four experiments. Here, participants were asked to use the questionnaire to evaluate a total of nine interaction components used in a mobile phone, a room thermostat, a web-enabled TV set and a calculator. The applicability of the questionnaire is discussed in the setting of a new usability study of an MP3 player. The findings suggest that at least part of the perceived usability of a product can be evaluated on a component-based level.

This paper presents the results of a meta-analysis carried out on the results of six experiments to support the claim that component-specific usability measures are on average statistically more powerful than overall usability measures when comparing different versions of a part of a system. An increase in test effectiveness implies the need for fewer participants in usability tests that study different versions of a component. Three component-specific measures are presented and analyzed: an objective efficiency measure and two subjective measures, one about the ease-of-use and the other about the users' satisfaction. Whereas the subjective measures are obtained with a questionnaire, the objective efficiency measure is based on the number of user messages received by a component. Besides describing the testing method, this paper also discusses the underlying principles such as layered interaction and multiple negative-feedback loops. The main contribution of the work described is the presentation of component-based usability testing as an alternative for traditional holistic-oriented usability tests. The former is more aligned with the component-based software engineering approach, helping engineers to select the most usable versions of a component.

This paper describes an experiment to determine which personality characteristics can be used to predict whether a child will make an effective participant in a user test, both in terms of the number of identified problems and the percentage of verbalised problems. Participant selection based on this knowledge can make user testing with young children more effective. The study shows that the personality characteristic Curiosity influences the number of identified problems; a combination of the personality characteristics Friendliness and Extraversion influences the percentage of verbalised problems. Furthermore, the study shows that selection of children based on these criteria does not lead to finding an unrepresentative sample of the product's problems.

Current usability evaluation methods are essentially holistic in nature. However, engineers that apply a component-based software engineering approach might also be interested in understanding the usability of individual parts of an interactive system. This paper examines the efficiency dimension of usability by describing a method, which engineers can use to test, empirically and objectively, the physical interaction effort to operate components in a single device. The method looks at low-level events, such as button clicks, and attributes the physical effort associated with these interaction events to individual components in the system. This forms the basis for engineers to prioritise their improvement effort. The paper discusses face validity, content validity, criterion validity, and construct validity of the method. The discussion is set within the context of four usability tests, in which 40 users participated to evaluate the efficiency of four different versions of a mobile phone. The results of the study show that the method can provide a valid estimation of the physical interaction event effort users made when interacting with a specific part of a device.

Design and user evaluation of a multimodal interaction style for music programming is described. User requirements were instant usability and optional use of a visual display. The interaction style consists of a visual roller metaphor. User control of the rollers proceeds by manipulating a force feedback trackball. Tactual and auditory cues strengthen the roller impression and support use without a visual display. The evaluation investigated task performance and procedural learning when performing music programming tasks with and without a visual display. No procedural instructions were provided. Tasks could be completed successfully with and without a visual display, though programming without a display needed more time to complete. Prior experience with a visual display did not improve performance without a visual display. When working without a display, procedures have to be acquired and remembered explicitly, as more procedures were remembered after working without a visual display. It is demonstrated that multimodality provides new ways to interact with music.