Special states (2)

Gregor Hagedorn G.Hagedorn at BBA.DE
Fri Mar 21 15:19:36 CET 2003

> 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 Hagedorn (G.Hagedorn at 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!

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