Interaction Support

Abstract

A graphic is not "drawn" once and for all; it is "constructed" and reconstructed until it reveals all the relationships constituted by the interplay of the data. The best graphic operations are those carried out by the decision-maker himself. Bertin (1981, p. 16) The previous chapter discussed various options for designing visual representations that help people in understanding time and time-oriented data. 'Seeing' trends, correlations , and patterns in a visual representation is indeed a powerful way for people to gain knowledge from data. However, we have also seen earlier in this book that manifold aspects are involved in the generation of a visual representation: characteristics of time and data, user tasks, choice and parametrization of visualization techniques, and so forth. Particularly when feeding unknown data into a visualiza-tion method, the visual outcome might not turn out as expected. But we usually do not know exactly what it is that is expected or whether the visual representation is effective with regard to the task that the user is trying to accomplish. And because there are things that we do not know, we have to seek assistance from the user. So, visual exploration and analysis is not a one-way street where data are transformed into images, but in fact is a human-in-the-loop process controlled and manipulated by one or more users. Having said that, it becomes clear that in addition to visual methods, a high degree of interactivity and advanced interaction techniques for working with time-oriented data are important. Interaction helps users in understanding the visual mapping , in realizing the effect of visualization parameters, in carving out hidden patterns , and in becoming confident about the data. But interaction also provokes curiosity users want to get their hands on their data-which is particularly useful when exploring unknown data. The importance of interaction is nicely reflected in the following statement: Visual representations alone cannot satisfy analytical needs. Interaction techniques are required to support the dialogue between the analyst and the data.