Depictions, such as maps, that portray visible things are ancient whereas graphics, such as charts and diagrams, that portray things that are inherently not visible, are relatively modern inventions. An analysis of historical and developmental graphic inventions suggests that they convey meaning by using elements and space naturally. Elements are based on likenesses, "figures of depiction" and analogs to physical devices. Spatial relations are used
metaphorically to convey other relations, based on proximity, at nominal, ordinal, and interval levels. Graphics serve a variety of functions, among them, attracting attention, supporting memory, providing models, and facilitating inference and discovery.
