At 04:26 PM 01-12-99 +0100, Gregor Hagedorn wrote:

...

There is a containment hierarchy (e. g. a flower contains petals)

which

...

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,

Peter

P. Hovenkamp Rijksherbarium, Leiden The Netherlands hovenkamp@rhbcml.leidenuniv.nl http://rulrhb.leidenuniv.nl/