Types of data

[Don Kirkup]

Kevin Thiele wrote;

> This worries me.  Is the entity/property/value schema restricted to 3
> levels? (ditto for XMLs element/attribute/value). If so, it seems too much
> of a straightjacket, especially if we want to express a hierarchy of
> elements like this.

No not at all, theoretically you can have as many levels in the hierarchy
you like;
element/element/...nth element/attribute/value

> What to do about
> leaf/lamina/abaxial_surface/vein_islands/indumentum/density.

One (RDF centric) way to model this would be to treat leaf, lamina,
abaxial_surface, vein_islands, indumentum as nested elements, and an
attribute called density which will have a value (let's say "sparse");

<My_description>
   <leaf>
      <lamina>
         <vein_islands>
            <indumentum density="sparse"/>
         </vein_islands>
      </lamina>
   </leaf>
</My_description>

or more in line with the conventional (DELTA, NEXUS) approach, simply as a
single element with an attribute (called density) and a value;

<My_description>
        <leaf_lamina_abaxial_surface vein_islands_indumentum density="sparse"/>
</My_description>

In the latter case you've lost a lot of contextual information, but the
approach (elements have properties that have values) might still offer
improved consistency in definition of descriptors .
Many of us, probably quite naturally, end up defining characters in this
way, but there are may examples to the contrary, and none of the existing
formats seem either expect or enforce this discipline.

don