We describe a meta-notation devised to express the major structural characteristics in widely-used data visualizations. The
meta-notation consists of unary and binary operators that can be combined to represent a visualization. Capturing structural
features of a visualization, our meta-notation can be applied to match or compare two visualizations at a conceptual level.
For example, a user's request for a visualization can be compared with visualization tools' presentation capabilities. The
design of the operators is discussed as we present their underlying concepts and show examples of their use. To illustrate
how expressive the meta-notation is, we explore some commonly-used data visualizations. A benefit of our approach is that
the operators define a set of required capabilities on which a visualization system can be organized. Thus, the meta-notation
can be used to design a system that interconnects various data visualization tools by sending and receiving visualization
requests between them.