Some terms related to diagrams (and also to design) strategies, language, layout, and so on are often misused or misunderstood:
– When is a diagram simple?
– When a diagram is simple is because it has few elements… and when it has more elements it becomes complex and less clear..
– Additional information is useless and complicated the message…
– Is additional information irrelevant?
– To make simpler a diagram, the best solution is to delete elements…
These terms are simplicity, complexity, clarity, additional, and irrelevant.
Simplicity. The Oxford dictionary defines simplicity as something being free from complexity or intricacy and absence of ornament. Shedroff (2007) synthesises these concepts explaining that clarity deals with one particular message or goal at a time, rather than the communication of everything at the same time; and that simplicity is misused producing meaningless messages rather than clarifying them. Referring to the concept of design simplicity, Per Mollerup (2005) talks about minimalism. He explains that minimalism deals with the fact of having few elements: simplicity of elements, number of element types, number of elements, and their size. However, both Bertin (1983) and Tufte (1990) explain that simplicity can be reached with an appropriate information organization, rather than with a low number of elements.
Complexity. Complexity deals with the number of dimensions (informational variables, level of reading, levels of information) that can be represented on a 2D design. Similarly than simplicity, something complex is not related to the number of graphic elements employed in a diagram, but with how they relate to each other.
Tufte (1983) describes a diagram as complex when it contains multiple layers of information that create multiple viewing depths and multiple viewing angles. He adds that complex diagrams need to have at least three viewing levels: 1) general structure: What is seen from a distance as a summary of the content, first level of content analysis; 2) main structure: What is seen up close as the primary idea of the content, second level of content analysis; and 3) hidden structure: What is seen implicitly and is understood besides the diagram itself, third level of content analysis.
High-information graphics combine several layers of close reading with an overview.
Clarity. Clarity is defined as the quality of being clear, distinct and easily perceived or understood and free from ambiguity. Clarity deals with the kind of message that a diagram communicates, focussing on the content, and not in the quantity of elements used to represent that content. The number of elements is not a parameter of clarity. A diagram can have only few elements but if all of them are at the same visual level with equal values, equal textures, equal colours, equal shapes, as a result there would be failed communication. When everything is emphasised, nothing is emphasised. If, on the contrary, a diagram has a high number of elements but well organised and differentiated, the result would be an extremely clear diagram. I believe that Tufte’s (2007) definition about this concept is undeniable. He states that ‘it is not about how much of empty space there is, but rather how it is used. It is not how information there is, but rather how effectively it is arranged’.
Additional. The Oxford English Dictionary defines additional as something extra, something that complements, enriches or improves a main subject. Tufte calls ‘evidence’ the information that adds details and enriches a diagram. A difference of meaningless information, additional information can sum details from multiple sources and levels to a diagram. Diagrams that contain additional information do not rely in one type of data or stay at one level of analysis. Detailed information helps to explain a complex content of a diagram, and makes it easier to understand. Furthermore, additional information enriches reading and amplifies content. Tufte suggests that for clarifying, the answer is to add details.
However, it is important to notice not additional information is considered useful. Mollerup explains what redundancy means. He argues that when additional information is purposefully used, it becomes meaningful information, eventhough it can be redundant. Furthermore, he adds that sometimes a message with no additional information is extremely vulnerable to misunderstanding. Nevertheless, not all additional information qualifies as useful redundant information. Sometimes, much additional information is just useless. As an example, both Mollerup and Wurman (2001) classify fashionable and trendy graphic ideas as additional information that causes graphic noise, has no useful meaning and makes the information less understandable.
Irrelevant. On the contrary, irrelevant is defined as something that is not pertinent or applicable, or not closely connected or appropriate to the matter being considered. Irrelevant elements are unnecessary elements. Moreover, a big difference with additional/detailed information, when unnecessary information is given more than once, it becomes meaningless and redundant.
– Bertin, J. (1983). Semiology of Graphics. Diagrams, Networks, Maps. UK: The University of Wisconsin Press
– Mollerup, Per (2005). Wayshowing : a guide to environmental signage : principles & practices. Baden : Lars Müller
– Shedroff, N. (1994). Information Interaction Design: A Unified Field Theory of Design. http://www.nathan.com/thoughts/unified/index.html [accesed on 14th September, 2009]
– Tufte, E. (2006). Beautiful Evidence. Cheshire, Connecticut, USA: Graphic Press.
– Tufte, E. (1990) Enviosing Information. Cheshire, Connecticut, USA: Graphic Press.
– Tufte, E. (1983). The Visual Display of Quantitative Infornation. Connecticut, USA: Graphic Press.
– Tufte, E. (1998) Visual Explanations. Cheshire, Connecticut, USA: Graphic Press.
– Wurman, R.S. (2001) Information anxiety 2. Expanded & updated ed. Indianapolis, Ind. : Que
Bridging Theory and Practice 