Gregor writes: "All these special states apply to entire characters. SDD currently provides no mechanism to express partial knowledge within a character (e. g. to score one state as not applicable, but another as present). Theoretically it is possible that a character is only partly entered, but this is not likely in a well designed terminology (it does happen where character clusters are combined into pseudo-characters, but such a design is considered problematic)."

Not so. One important difference between Lucid and DELTA is that DELTA can only encode uncertainty for a whole character, Lucid only for a character state. Often in Lucid we do encode uncertainty for an entire character (for example, fruit colour is uncertain for a given taxon because fruits are unknown) - we do this by (slightly messily) encoding uncertainty for all the states of the character:

Fruit colour (coding for taxon x) red - UNCERTAIN yellow - UNCERTAIN pink - UNCERTAIN white - UNCERTAIN ....etc

Regarding Uncertainty: I propose to use modifiers on states for this purpose (see the chapter in Special states: "Not supported as special state, but supported through modifiers" and the linked document on "Uncertainty modifiers"). That is, Uncertainty is NOT a special state as discussed in the paragraph quoted at the start.

The question is: Is it necessary to code "unfinished work" or "not applicable" against states? This is not a trivial decision. Making Unknown/not applicable statements realtive to states means that any change in the state terminology requires a revision of all descriptions using that character. If the character is a true atomic entity, I believe it is easier to enforce that these statements are character level statements, not modifiers.

I believe that the attempts to use "unfinished work" or "not applicable" usually show we are dealing with "pseudo-characters" like distribution. Does anybody have a good case with real descriptive, chemical or morphological data? Stuff like "enzyme tests" I really consider an assemblage of characters, which will be much less painful to handle appropriately as soon as character groups and hierarchy are present. Currently people like to keep these in one character, because that is the only hierarchy readily available for organizing the work.

Gregor ---------------------------------------------------------- Gregor Hagedorn (G.Hagedorn@bba.de) Institute for Plant Virology, Microbiology, and Biosafety Federal Research Center for Agriculture and Forestry (BBA) Koenigin-Luise-Str. 19 Tel: +49-30-8304-2220 14195 Berlin, Germany Fax: +49-30-8304-2203

Often wrong but never in doubt!