Comparative data

Mike Dallwitz md at ENTO.CSIRO.AU
Wed Sep 6 11:57:25 CEST 2000

> From: Kevin Thiele <kevin.thiele at PI.CSIRO.AU>

> I think part of the basic problem [with DELTA] is that it's tried to force
> too much structure and while this is a great promise it's been an
> impediment in practice.

This is the problem with (or the virtue of) all character-based data systems
(although DELTA does alleviate it by allowing comments and text
'characters', as discussed previously). I agree with Kevin that it is an
impediment to acceptance of such systems. In fact, I think it's the main
impediment - producing comparative data is difficult. Nevertheless,
shouldn't this be one of the main objectives of taxonomy?

Thirty years ago, Leslie Watson wrote:

    Perusal of the average taxonomic-descriptive work usually reveals that
    _as a source of comparative data_ it is hopeless. One genus will be
    described in terms of criteria that receive no mention in the next. Even
    species of the same genus may be described inconsistently. It is often
    impossible to distinguish with any degree of conviction between actual
    observation and extrapolation, between absence of a feature and mere
    failure to seek or comment on it. In general, the further one proceeds
    up the hierarchy, the less comparative the descriptions become. Given
    the situation prevailing in individual publications it is not surprising
    that scanning across them is even less satisfactory. ... If facts are
    wanted for reviewing the classification of a large group it is
    singularly disheartening to have to seek them in miscellaneous works of
    this kind. The labour is immense; worse, one sets out with the
    depressing knowledge that much of it will be wasted on discovering that
    the details thus compiled are not comparative. There is a welter of such
    material theoretically applicable to most major taxonomic problems,
    which will probably never be called upon because of its unpromising
    presentation and sheer intractability.

    L. Watson (1971). Basic taxonomic data: the need for organisation over
    presentation and accumulation. Taxon 20, 131-136.

Things haven't improved much since, and they won't if we back away from
teaching and strongly encouraging people to produce comparative data.
Marking up free text into related chunks and making it available in
electronic form would certainly reduce some of the labour, referred to
above, of the person who is searching for comparative data. But it would not
make non-comparative data comparative, and doing the markup would be a
difficult and probably thankless task.

I think that, in addition to the classificatory problems alluded to above,
the majority of nomenclatural problems (proliferation of synonyms) are the
result of not having readily accessible, comparative data.

> It seems to me that the main limitation of DELTA isn't simply ... that
> it's not complex enough.

I'd say that that's exactly the problem - for 'not complex enough', read
'doesn't have enough features'. Of course, to add new features in the best
way, and to minimize the complexity in some sense, you might have to abandon
existing data structures. However, we should not throw the baby out with the
bathwater. That is, we should retain the useful features of current systems.


Mike Dallwitz

CSIRO Entomology, GPO Box 1700, Canberra ACT 2601, Australia
Phone: +61 2 6246 4075   Fax: +61 2 6246 4000
Email: md at  Internet:

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