Stuart Poss wrote:
Are existing methods and this discussion restricted to "morphological characters"?
Personally I think that morpho-anatomical characters are not sufficiently different from other character like those mentioned in Stuarts post. I would want to discuss them here as well.
Interesting things may, however, happen regarding character types. Besides an expanded list of character types (including date/time, ordered categorical: linear, cyclic, tree, or complex/reticulate) new types may appear.
A new type that I am specially interested in, is the "alignment" type. A while ago on DELTA-L somebody commented that alignments can principally be treated as a group of categorical characters, just as they are in NEXUS. However, I believe this treatment is not adequate for the following reasons:
o the homology of these characters is dependend on the alignment, especially: o adding new items (sequences) may change the homology assumptions within the remaining sequences o the naming/identification of characters would be extremely difficult to handle, because a base position depends on the alignment
I believe that these special considerations require a special character type for aligned sequence data
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What other character types do you think are necessary?
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Whether images/audio/video material etc. should be considered character, I am doubtful. I currently prefer to summarize them together with formatted text documents and database access (information systems/Identification or query interfaces) or any other URLs as "external resources". I am not as clear about this as I would wish. One criterium could be that analytically accessible, well structured information should be considered a character (thus including restricted vocabulary text information, e.g. "lists") whereas only human usable resources should be treated different.
Vector graphics lie somewhere in between... I appreciated the recent contributions about the parameterizations of shapes, I think this will be helpful!
Gregor
---------------------------------------------------------- Inst. for Plant Virology, Microbiology, and Biosafety Federal Research Center for Agriculture and Forestry (BBA) Gregor Hagedorn Net: G.Hagedorn@bba.de Koenigin-Luise-Str. 19 Tel: +49-30-8304-2220 14195 Berlin, Germany Fax: +49-30-8304-2203
Often wrong but never in doubt!