|InfoVis.net>Magazine>message nº 188||Published 2007-05-12|
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Mendeleev had no idea (we think) of Information Visualisation, but he definitely had a vast knowledge of Chemistry, his profession. The 19th century was very prolific in regards to the discovery of chemical elements and their associated properties. As different researchers were discovering new elements and the computation of atomic weight was being refined, many interesting coincidences were being discovered too.
The work of different researchers had identified the fact that certain groups of elements had similar properties. Metals, for example, had a characteristic shininess, high conductivity both thermal and electrical and the tendency to combine with oxygen to produce oxides. The lapse between 1850 and 1865 was particularly fruitful in the discovery and characterisation of new elements. This gave rise to different taxonomies based on the similarity of their properties, like the triads of Döbereiner and Newland's octaves. So by 1869 there were already many pieces of the chemical elements puzzle.
Mendeleev had been studying their properties which he summarised in the following Periodic Law:
The properties of the chemical elements aren't arbitrary, they depend on the structure of the atom and vary according to atomic weight in a periodic way.
Later on it was discovered that it was not the atomic weight but the atomic number* which defined the periodicity , but this subtlety is out of the scope of this discussion. The fact is that Mendeleev decided to follow the scheme of Newland's octaves, that ordered the elements into 8 columns according to increasing atomic weight, but correcting some of their limitations, among them:
From the use of the table we can derive three important features:
These three properties are typical of any good visualisation and have converted the periodic table in an example of excellence in information visualisation.
Maybe due to this and to the fact that the table is very well known since it plays a part in many curricula of secondary schools worldwide, you can find many attempts to use its layout as a way to visualise any type of classification, with greater or lesser success.
Among them you can find the "Table of Condiments that Periodically Go Bad", listing condiments along with their nominal duration as consumable stuff, or the "Table of Desserts" that lists a set of desserts in a Periodic Table fashion. Much more recently appeared a Periodic table of Visualization Methods in visual-literacy.org due to the work of two researchers of the University of Lugano, in Switzerland. You can see the rationale behind it as a PDF document in "Towards A Periodic Table of Visualization Methods for Management".
Despite the good work in classifying more than a hundred different visualisation methods, using the scheme of the periodic table and the exact shape of the same for displaying the methods is more than disputable since the paradigm the periodic table adheres to (atomic number, chemical properties, orbitals, etc) has no parallelism to the case of visualisation methods, which invalidates the visual metaphor it intends to be. Stephen Few discusses this point very cleverly in his blog Visual Business Intelligence. Hence I will not abound on this here.
The fact is that mimicking existing paradigms just because they provide a familiar lay-out doesn't add any insight into what we are looking for, that is regularities in the methods of visualisation. Trying to map the regularities of the chemical elements into those of desserts, or visualisations, is misleading since it hampers finding true regularities and although it covers the transmission of knowledge it doesn't contribute to pattern detection and even less to knowledge discovery, outstanding outcomes of Mendeleev work.
Building a taxonomy of visualisation methods is not a simple issue and having an equivalent of the in depth work done by Mendeleev for chemistry in Information Visualisation would be a major advance, that, in my opinion we should pursue by finding the main features of each method, building a new paradigm and representing them in original and meaningful ways in accordance with said paradigm.
Incidentally a good reference for visualisation methods in information graphics is Harris' Information Graphics
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