  Visualization researchers and visualization professionals seek appropriate
abstractions of visualization requirements that permit considering
visualization solutions independently from specific problems. Abstractions can
help us design, analyze, organize, and evaluate the things we create. The
literature has many task structures (taxonomies, typologies, etc.), design
spaces, and related ``frameworks'' that provide abstractions of the problems a
visualization is meant to address. In this viewpoint, we introduce a different
one, a problem space that complements existing frameworks by focusing on the
needs that a visualization is meant to solve. We believe it provides a valuable
conceptual tool for designing and discussing visualizations.
