(RQT) Character and item hierarchy

P.Hovenkamp Hovenkamp at NHN.LEIDENUNIV.NL
Thu Dec 2 09:43:34 CET 1999

At 04:26 PM 01-12-99 +0100, Gregor Hagedorn wrote:
>> There is a containment hierarchy (e. g. a flower contains petals)
>> raises no problems in XML.
>I would like to challenge this assumption, which seems to be
>generally accepted in the discussion here.
>Thus: there are multiple concurrent or competing hierarchies, which
>may overlap.
>*** Call for more examples: Can anybody come up with more good
>examples (perhaps from animals) as to why a fixed hierarchy in the
>form of a feature path may be unpractical?

Here's my example:

In ferns, leaves are often highly divided, into pinnae, pinnules, segments
and even lower order elements. In most descriptions, a clear hierarchy is
implied: pinnae are part of leaf, and inherit the properties, pinnules are
part of pinnae and inherit...

Programmers may be tempted to hard-code this hierarchy.

However, for many characters, an opposite hierarchy can be devised, which
may be much more informative: ultimate segments have margin, veins, and
properties of those, which are inherited in the penultimate elements, and
then onwards to the leaf. Especially in species where degree of dissection
varies strongly (they occur), this may be a much better way of descibing a
fern leaf.
Hard-coding the usual hierarchy of leaf, pinnae, pinnules may therefore
stand in the way of understanding and describing fern morphology.

Is that clear enough for non-fern people?

Best wishes,


P. Hovenkamp
Rijksherbarium, Leiden
The Netherlands
hovenkamp at rhbcml.leidenuniv.nl

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