I have to think about the applicable/inapplicable stuff.

2. I recently had a good discussion with Wouter Addink and Flip Boer

in Holland. Among other things we considered whether a structural hierarchy (leaf stalk is part of leaf is part of plant) could replace dependency rules. Clearly, it can replace some rules: if there is no leaf, all leaf characters will be inapplicable. However, it can not replace depencies based on multiple states that are not present/absence. Further, it may not always be true because we tend to use confusing terminology: Something at the leaf stalk base would belong to leaf stalk, but absence of leaf stalk (i.e. absence of measurable lenght of leaf stalk) does not imply absence of stalk based characters. Any further ideas on this?

I see it as more object oriented rather than heirarchical. A plant has properties root, stem, leaf, inflorescence. Each of which can also have properties. A leaf has color, shape, pubescens etc. If "pubescence" is defined in a general way, it doesn't need to be redefined each time an object can possess pubescens. Just the once should be sufficient.

In the case of your above example, I would tend to make "stipules" a property of "leaf" rather than "petiole." The leaf could have properties "blade," "petiole," and "stipule;" where each would also possess certain properties. Normally, the way that you defined things, stipule characters couldn't exist if they're tied to the petiole.

Susan Farmer sfarmer@goldsword.com Botany Department, University of Tennessee http://www.goldsword.com/sfarmer/Trillium