Character types (RQT)
G.Hagedorn at BBA.DE
Mon Nov 29 17:28:00 CET 1999
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,
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
I believe that these special considerations require a special
character type for aligned sequence data
What other character types do you think are necessary?
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!
Inst. for Plant Virology, Microbiology, and Biosafety
Federal Research Center for Agriculture and Forestry (BBA)
Gregor Hagedorn Net: G.Hagedorn at bba.de
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