On visual stability and visual consistency for Progressive Visual Analytics

The emerging field of Progressive Visual Analytics (PVA in what follows) deals with the objective of progressively create the final visualization through a series of intermediate visual results, affected by a degree of uncertainty and, in some cases, a non monotonic behaviour. According to that, it is a critical issue providing the user with no confusing visualization and that results in a novel point of view on stability and consistency. This position paper deals with the novel and challenging issues that PVA poses in term of visual stability and consistency, providing a preliminary framework in which this problem can be contextualized, measured, and formalized. In particular, the framework proposes a set of metrics, able to explore both data and visual changes; a preliminary case study demonstrates their applicability and advantages in adequately representing data changes in a visualization.