In signs, one sees an advantage for discovery that is greatest when they express the exact nature of a thing briefly and, as it were, picture it; then, indeed, the labor of thought is wonderfully diminished. Gottfried Leibniz

Leibniz’s quotation is prescient on the value of visualization, but it doesn’t tell the whole story. As it turns out some concepts are better expressed verbally than visually. Here are some rules of thumb inspired by Colin ware’s Visual Thinking for Design:

• language is better-suited for expressing complex, logical relationships and abstract ideas
• diagrams are better-suited for expressing gist, spatial structure and relationships between objects

To see these heuristics in action, think of the class hierarchy in your favorite programming language. The hierarchy is all about how entities relate. as such, it comes across beautifully in diagram form (look no further than UML). Now try to express a for loop with a diagram. Tough, isn’t it?

Failure to choose the appropriate medium for information leads to weak products. Several visual programming languages failed because diagrams of conditional relationships are not as clear or succinct as the corresponding text. a complete semiology of “graphics” will therefore include an understanding of when not to use images, and instead to substitute text.

I should note that language and diagrams can be connected via deixis (e.g. a finger pointing at the moon; see ware’s book for more), and that chris weaver has a new paper on exploring multi-dimensional data with visual boolean queries, conjunctive visual forms.