The end of DELTA?

Don Kirkup d.kirkup at RBGKEW.ORG.UK
Mon Nov 22 17:06:31 CET 1999


The proposition I think is that (at some level) it is desirable to transfer
data between formats (such as DELTA, NEXUS or LUCID). If this is the case
then there are difficulties that need addressing, specifically the loss of
information that occurs.
To some extent the different formats do deal with different subsets of
'descriptive' information, for example you might argue that characters used
in phylogenetic analysis are defined differently from those used in
identification programs. Nevertheless, there are still areas of overlap
between two or more of the exisiting standards that are not currently
supported by the available import/export routines (eg. character
dependencies to name one).

The approach of amalgamating (what some might regard as) the 'proprietary'
formats into a single 'superstandard' wasn't much favoured since that would
only provide only for exisiting functionality.
What was talked about at the TDWG meeting was to take a step back from
existing standards in order to look at the whole area of descriptive data in
the broadest sense (and for my money that includes marking-up or tagging of
descriptive texts).
As Gregor has already summarised elsewhere, the first step of the discussion
should be a requirement analysis, the second the possible use of XML as a

On the subject of the latter, XDELTA looks to me to be a straight
representation of (a subset of) the DELTA standard in XML. While this does
open up the scope for parsing, it isn't necessarily the approach I was
thinking of.

For example, how could retrieval of descriptive information across a
department or institution be facilitated? Is it because of the sheer
flexibility in how the characters can be defined using DELTA, that querying
across projects is difficult to say the least, unless the character set is
global that is (and therefore with a lot of redundacy)?

Can character definitions be constrained without making too tight a
straight-jacket for oneself? Might it be possible to represent taxon
character descriptors by for example an entity/property/value (eg.
leaf/shape/ovate) based schema?
This on the face of it would seem to map onto an XML element/attribute/value
schema pretty well. Would that help define more closely how we construct
characters and maybe even prove universally applicable for all character

Could one constrain further by expressing within the schema the hierarchical
relationships between the elements(eg 'blade' and 'petiole' as child
elements of leaf') or would the introduction of terminology into the
'standard' be a step too far?


Dr Don Kirkup

> Dear Computer Taxonomists,
> Greetings, and welcome to the new discussion list...
> As an attempt to start a discussion, I am posting this to ask: do we all
> really agree that there should be a new standard for descriptive data
> based on XML, as a substitute for DELTA (as well as NEXUS and XDF)? Or
> should we instead just try to improve one of the existing formats? As of
> myself, when I first read the specifications of "XDELTA", I was under
> the impression that in some way the DELTA format as we know it would
> then become obsolete... But what of NEXUS, or XDF? Has anyone considered
> of the integration of these formats plus DELTA into a single new,
> XML-based, format for descriptive data?
> Just "food for thought"...
> Best wishes,
> --
> + - - - - - - - - - - - - Mauro J. Cavalcanti - - - - - - - - - - - - +
> | Setor de Paleovertebrados, Departamento de Geologia e Paleontologia |
> |                      Museu Nacional do Rio de Janeiro               |
> |      Quinta da Boa Vista, 20940-040, Rio de Janeiro, RJ, BRASIL     |
> |                     E-mail: maurobio at                    |
> |           Home Page:           |
> + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
>       "Life is complex. It consists of real and imaginary parts."

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