Thoughts on taxonomy development

The following comments may contribute to the discussion started during the call today.

I think we should consider a taxonomy that can accommodate a broad class of graphical representations. Data visualization appears to have gained the focus of attention in the analysis so far, but it comprises only part of the entire range of possibilities that a well designed taxonomy should cover.

Graphs (as in vertices and edges) have been at least introduced by way of the reference to the SVG Connector work. Maps are a subset of graphs, as are many other types of diagrams. Then there are graphics based on geometric figures, as would appear in geometry texts. There are also images of objects and scenes, occupying a different category from the preceding cases.

A further category is that of data visualization, graphs (as in subsets of the complex plane etc.) of mathematical functions, and so on. I think we should take a broad approach to begin with, establish which categories we plan to work on for purposes of the first version of the taxonomy, and proceed to the details.

There has also been interesting discussion as to what kind of information the taxonomy should capture. In particular, a question has been raised regarding whether we should concentrate on the data to be represented, or on how they are represented visually in the SVG. I think a strong argument can be made for providing detail at both of these levels, and indeed it isn't clear that the levels are easily distinguished. An advantage of using properly marked up SVG is that various types of information can be preserved in the markup, without requiring the author to choose the terms in which to describe the graphic. In a textual description, however, such editorial choices generally have to be made, and this can be more or less problematic depending on the context of ultimate delivery to the user.

For instance, an engineering or physics student who is accessing a circuit diagram is likely to be interested in high-level information about the components and their respective interconnections. However, the student may also wish to know how the symbols for various components in the circuit are represented, i.e., through what graphical conventions. A good approach to accessibility would allow the user to choose to interrogate the graphical representation at this level, which is much closer to that in which the SVG itself is written. To summarize, the user may want to know about lines, curves, polygons etc., in addition to resistors, diodes, transistors etc. Accessible vector graphics formats offer the opportunity to add meaning at various levels of description; and I think we would be missing a great part of the benefit if we did not allow for different strata of detail to be included.

I think of the issue of graphical representation in terms of inferences: there are geometric facts about a graphic which, combined with the conventions applicable to the kind of graphic in question, justify conclusions about whatever is represented. I think we need to make explicit (in the taxonomy, the states and properties) the premises of those inferences as well as the conclusion, so that the user who needs to know can query everything from relatively basic geometric properties through to properties of the data or objects depicted.

Perhaps we should separate the problem of devising an extensible and appropriate taxonomic hierarchy from that of what details we want to fill in for the first release.


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Received on Friday, 19 December 2014 21:38:11 UTC