"Lev Manovich is one of the big names about theory of new media, and he also talks about visualization. Now, he publish a new aricle called What is Visualization. You can read it all clicking on the name of it, But here you are some sentences I'd like to highlight:
"300 years after William Playfair amazement at the cognitive power of information visualization, it looks like that finally many others are finally getting it."
"Let's define information visualization as a mapping between discrete data and a visual representation."
"Scientific visualization and information visualization come from different cultures (science and design); their development corresponds to different areas of computer graphics technology."
"Information design works with information, while information visualization works with data."
"When we switched from pencils to computers, this did not affect the core idea of visualization(...). Similarly, while availability of computers led to the development of new visualization techniques (scatter plot matrix, treemaps, etc.), the basic visual language of infovis remained the same as it was in the 19th century"
"The practice of information visualization from its beginnings in the second part of the 18th century until today relied on two key principles. The first principle is reduction (...). The second is spatial variables."