Why do we need a taxonomy?
The authors claim that a good taxonomy can “guide users” as well as guide “research”, which I basically agree. In addition, in terms of research, understanding and utilizing a taxonomy is not just about labeling one’s research, but more about making it more clear what you are working on. Knowing what your research is and is not about can better help you build a firm understanding into it.
Design Model vs. User Model
Both design model and user model are about the assumptions made about the data. The difference is: design model is more about the nature or attributes of the data while user model is more about the purpose of visualizing such data.
Given vs. Chosen
This is the main criterion for the high-level taxonomy. However, the paper does not offer explanations about these two terms. Reading Munzner’s talk slides does not help a lot. In my opinion, ‘given’ means the object of study is integrated, coherent and undecomposable while ‘chose’ means the object of study is selected from a larger or broader concept or entity.
A pipeline-like view of visualization
The four concepts proposed in the paper also mark the four critical stages in the visualization pipeline, namely, identifying object of study, collecting data, developing design model and developing user model. (Also the relationships shown in Figure 1. is very enlightening)
Why does the taxonomy happens in the design model? The Object of Study stage is too high-leveled, making it loosely related to the actual research of visualization. The Data stage is too low-leveled – the same data set can be mapped to various design models and user models, making it ambiguous as which category to fall into. The User Model stage can serve as a candidate if we consider the taxonomy of visualization techniques instead of taxonomy of visualization. Looking back at the Design Model, which means the assumption made about the nature and attributes about the data, it seems that this stage lays between low-leveled data and high-leveled visualization purposes and techniques hence suitable for a taxonomy basis.
“Constructing a user model is a complex process that may include making assumptions about the data and the display algorithm, developing hypotheses, searching for evidence to support or contradict hypotheses, and refining the model.”
 Waern, Y., “On the Dynamics of Mental Models”, In Mental Modelsand Human-Computer Interaction 1, Eds. D. Ackermann and M.J.Tauber, Elsevier Science Publishing Company, New York, 1990, pp.73-93.