## 5 Experimental Analysis And Results
### Evaluation Criteria  
The experiments have been assessed quantitatively by a comparative analysis of instructors' access logs. Considering the same instructor and the same course, the baseline for comparison of the usage of the proposed interface is the usage of log referring to objects (i.e., learning objects and modules instances) before the introduction of visual monitoring metaphor. The log information is thus compared before and after the metaphor introduction, i.e., with and without the metaphor. In this way, since the original method of monitoring data analytics was used before and along with the three modifications, the original method can be thought of as a type of control for the study. The instructors used all the tools at least once a week for an initial period of two weeks, after which they were free to choose and switch among any of the three metaphors (i.e., _Thermometer bar, Dimensional morphing, Tag cloud_) or the traditional log reports. The objective data are sufficient for assessing an adequate evaluation of the tool. We decided to ask some questions to educators to understand eventual issues of the visual metaphors better, aiming at future enhancements. At the end of the experimental phase, the instructors were asked to fill a questionnaire for a qualitative evaluation of their experience (included in Appendix A). The screened parameters included the general usability assessment of the interfaces, their usefulness regarding the course management, the impact on the teaching strategy, the comparison to traditional methods of user monitoring. For each morphing metaphor, we proposed questions about how much the visualisation usability is perceived (e.g., easy to activate, easy to use, usable as a monitoring tool) and about the frequency of use (e.g., how often it has been used and in which phase of the course it has been used most, if during or after the lectures). Finally, an overall evaluation of the tool has been proposed. Users could answer in qualitative evaluation using a Likert scale [30] with five items (i.e., 1 to 5, where 1 is low and 5 is high). The final evaluation is thus composed both of subjective data from the teachers' questionnaire, and objective data from users logs. To ensure the quality and accuracy of the answers, the questions are redundant and are used as a check to identify contradictions, such as a positive assessment of usability and usefulness along with a negative overall assessment. Consistency has then been verified with the usage logs of the metaphor declared as preferred. The results show that the educators' responses were consistent. Figure 3 shows an example of usage, with the aggregation parameters selection panel. In this real case studied, the time window spans over one month. The _End date_ parameter is particularly important for that course. The second assignment was given to the students one week before the submission deadline. The temporal proximity was set one month after the end date to have a better  
Figure 4: Colour gradient. Figure 3: MonitorView parameter selection panel. colour distribution on the topics labels. In this use case, the instructor was looking at the usage status of learning objects to identify the resource material that students were reviewing to complete the assignment. The standard course view without any morphing is shown in Figure 5.  
Figure 6 shows the visualisation of the course page according to the _dimensional morphing_ metaphor with its time interval and the aggregation parameters shown in Figure 3. The icons and labels are stretched and coloured, considering the learning object popularity and the access temporal distribution. In Figure 7 the same data are shown in the _Bar mode_ following the _Thermometer Bar_ metaphor. A _Tag cloud_ is shown in Figures 8 and 9, where the information and page layout is morphed to obtain two different styles of the _Tag cloud_. In the first, the labels of learning objects are adapted in _Wordle_ style [31]; in the  
Figure 5: Standard course view with no morphing.