Types of data

P. F. Stevens peter.stevens at MOBOT.ORG
Wed Nov 24 09:52:29 CET 1999

>One of the data types that I would like to see modeled is a "matrix type"
>data type.  Consider the leaf shape.  When I made up my DELTA data set,
>I turned leaf shape into *3* characters -- one for leaf width, one for
>the position of the widest shape, and a 3rd for the contour of the
>sides.  (narrow, broad; ovate, obovate; rounded, parallel).  As the
>basis for this division, I used the IAPT plain shape chart -- a two
>dimensional representation.
>When you have a shape that varies from narrowly ovate to broadly obovate --
>how can you model that in *one* character?  Variance from narrowly ovate
>to narrowly obovate is possible just as variance from narrowly ovate to
>narrowly obovate.
>You would define the data type by number and size of dimensions.  (Two
>would probably be sufficient for most cases).

Of course, the IAPT shapes are not "real", they are conventions (the actual
circumscription of the various shapes was decided at a meeting back in the
'50s, I think).  As affording a communication device, the IAPT shape chart
is excellent, and exactly what is needed (see below), as a means for
measuring the world, it is definitely inferior to metrics such as
millimeters and degrees.  The states, the 0s and 1s, of phylogenetic
analyses, are treated far more as IAPT shape charts than as the results of
measured and analysed variation for my liking.  Ideally - and I stress
"ideally" - basic taxonomic data should be metric-type data (and images of
things like pollen surface, perhaps wood anatomy) linked to specimen,
rather as with d.n.a., where a sequence is deposited in GenBank and lnked
to a specimen.  I am not suggesting that all our taxonomic work should be
so anchored, but I am suggesting that far more than at present should be so
treated.  Many morphological data sets consists of little more than
unsubstantiated assertions about the world.  If, however, somebody asked me
for a flora treatment of some 'well" understood group for N. Amerias, I
would probably have no reasonable alternative (because one's life is
limited...) than to use whatever communication conventions exist for what I
am looking at.  (However, if a group had been monographed following more
ideal standards, think how easy it would be to produce local accounts of
variation, not to mention distribution maps, etc., etc.)

And thinking of things like terms used in describing organisms, there
certainly seems room for either synonymy tables and/or for more IAPT-type
conventions.  This is particularly true of genus- and family-"level"
descriptions in plants - for teaching purposes, I am reading descriptions
of genera and families in an edited compendium, and there may be three or
four words for what is arguably the same thing, or terms that acutally make
it more, not les, difficult, to get to grips with the basic variation.

Peter S.

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