Developing a dynamic usability framework for spatial domain applications

Lei Cui and Monica Wachowicz
Wageningen University and Research Centre
Centre for Geo-Information, The Netherlands

Researchers have adopted different approaches in specifying usability elements and their respective measures. As a result, there are over 40 usability elements proposed in the literature, and for most of them, there is a lack of specified measures. In particular, it is currently very difficult to identify a core set of fundamental techniques that clearly distinguish one usability element and its specified measure(s).One approach has been proposed in the early 1990s and it is based on a hierarchical set of usability elements named as learnability, flexibility, and robustness. Measuring these elements is based on evaluating the experience of the user when interacting with the interface. Other approaches have developed usability questionnaires which tend to cluster usability elements and measures such as speed, errors, time to learn, retention, flexibility, attitude, learnability, efficiency, retention, errors and pleasing ability, or accuracy, completeness, temporal, human and financial efficiency, comfort and acceptance (See www.usabilitynet.org/tools/r_questionnaire.htm for an overview).

It is our contention that fundamental advances in usability will depend as much on establishing a solid theoretical basis for a usability framework as it does on application of usability questionnaires and tests. In fact, there has not been sufficiently methodical evaluation of usability of commercial geoweb sites. Therefore, this paper describes our first attempt to develop a dynamic usability framework for spatial domain applications. It consists of five interrelated components, which are users, tasks, interaction modes, measures, and usability elements. The framework was applied to investigate the effects of map interactive displays on user satisfaction and familiarity across two types of commercial geoweb sites. Three tasks have been selected to allow users to search over a particular geographic location and return the results as a map image at a particular scale. We have also taken the system perspective by incorporating the efficiency, effectiveness, and operability as usability elements within the spatial context. Finally, the framework dynamically assign the measures (time spent, number of interactions and number of errors occurred to users when performing tasks) to the six usability elements (familiarity, efficiency, effectiveness, error rates, operability and satisfaction).

Towards the implementation of the proposed framework, a survey questionnaire was assembled to gather information about the profile of the target user group, and the purposes and general use of the geoweb mapping applications. The questionnaire was based on multiple choice answers which were related to three components of the usability framework (i.e. types of users, tasks, and interaction modes) Sixty-two respondents replied the questionnaire out of 200 questionnaires sent out. Data collected were analyzed to formulate a usability test based on usability elements and measures. The usability test was performed by eight users and the whole interview and users interaction with the interface were fully recorded.

The main results of the usability test confirm the dynamic characteristic of usability, and the important role of the framework for understanding and evaluating geoweb mapping applications. More research is needed to explore the potential classification of the framework components into hierarchies, where dynamic interrelations between sub-components can be defined through types of interaction modes. Finally, the use of two commercial geoweb sites has also suggested that there are more difficulties when employing the framework to understanding the content of interfaces, mostly due to the lack of studies on quantitative measures for content, which reveals one of the many topics to be further addressed based on the proposed dynamic usability framework.

Keywords: usability; dynamic usability framework; spatial domain; geoweb