Wolfgang Dzida

User-Perceived Quality of Interactive Systems

User-perceived quality of interactive systems is defined in terms of statistically nonoverlapping categories, so-called dimensions or factors Categories are identified by factor analysis and represent a dimensional concept of the quality of interactive systems as perceived by its users. Each category describes essential user requirements.

Making use of scenarios for validating analysis and design

Scenarios can help remedy the most serious obstacle in the design process that is a chronic lack of knowledge of the application domain. Moreover, scenarios can be employed in analysis and design to serve both illustrating the context of an envisaged usage (users perspective) and demonstrating the design proposal in terms of the intended usage (analysts perspective). In contrasting both perspectives by means of a dialectic process a synthesis can be achieved that incorporates a shared understanding. Validation is a process to achieve such an understanding. The semantic structure of types of scenarios is investigated thus illustrating how a context of use analysis according to ISO 9241-11 can be exploited for validation purposes. The role of scenarios in usability engineering is contrasted with traditional concepts of systems analysis as an attempt to narrow the bridge between software engineering and usability engineering.

The role of excursions in interactive systems

Abstract It is recommended that man—machine dialogue systems be designed so as to make them more self-explanatory, and hence more user-friendly, by the inclusion of a dialogue form called an excursion tour. This is defined as an information-gathering sequence of operations that enables the user to learn the commands which change his data sets, and which are called direct way commands. The distinction between the excursion and the direct way forms of dialogue is justified in terms of cognitive psychological theory, and corresponds to the distinction made there between planning and performance, or between knowing and doing. The operation of the two dialogue forms and their interaction is represented by an extension of the TOTE model of human task performance. The term interactive deadlock, or unsolvable incongruence, is introduced to denote the situation in which either no command exists that will further an essential subgoal, or if it does exist the user has no way of discovering it within the system. In terms of the TOTE model, it is shown how such deadlocks or incongruences that are unsolvable on one level may be overcome by extending the users knowledge with the help of excursions.

ERGO-Shell: a UNIX-interface for task preparation

The ERGO team investigated how software engineers manage the complexity of both the system and the task at hand, in particular during the preparation of work. The team found that prior analysis greatly enhances the effectiveness and efficiency of task completion, so much that it can be regarded as a prerequisite. In addition they found that preparation and planning of tasks is very difficult using traditional UNIX-shells. The team used Petri nets to brainstorm, design and communicate specifications for better solutions. The result was a set of well-defined requirements for redesigning user problem solving in UNIX and, in answer to these requirements, ERGO.

Der Arbeitskontext als Komponente der Benutzerschnittstelle

Fur Benutzerschnittstellen an komplexen Anwendungssystemen wird eine Komponente entwickelt, die einen ausreichenden Transfer von Wissen uber die Anwendung des komplexen Systems sicherstellt. Es gilt, das Wissen von erfahrenen Benutzern so aufzubereiten and anzubieten, das weniger erfahrene Benutzer das reiche Funktionsangebot ebenfalls nutzen konnen. Andernfalls bleibt die Gefahr bestehen, das das Funktionsangebot eines Systems nicht genutzt wird und das System nicht wirtschaftlich eingesetzt werden kann. Das hier vorgestellte Konzept kann auf komplexe Konstruktionsarbeitsplatze beim CAD und in der Software-Entwicklung angewandt werden, soweit diese Arbeitsplatze auf der Basis von Unix entwickelt worden sind.