DELTA. Comments and opinions continue to trickle in.

Ingolf Askevold IASKEVOL at VM.CC.FAMU.EDU
Thu Mar 17 15:06:29 CST 1994

      Well, a few pretty strong comment about DELTA have come in
since I posted the last bunch of opinions I'd received, last week.
Perhaps these will generate some further discussion, for I think
it's informative and illuminating.
      Anyone, as have those who contribute below, who wants to
contribute to the commentary but wants to do so anonymously, may do
so through me.  Sure, I'll be the fall guy and take all the flack,
why not?
      Ingolf Askevold  iaskevol at

[these are not presented in any particular order.  I'm deleting the
names of those who sent me them, which some sort of even
requested... ]

[statements in [brackets] are those I've added to inject my opinion
or for clarification]

Date:         Tue, 15 Mar 94  16:56:06 EST

   So maybe I should confess to being a secret DELTA user!  A
little bit like one of the "groups" people attend these days.  I
have used it to create tables, keys, write texts (which I edited
rather heavily since I do not like the consequences of DELTA for
the written language).  I am in fact, using it all the time.  The
first DELTA files are very nearly always disastrous:  It takes time
to learn how to write a decent character-list, and certainly to get
it corrected etc.  However, once one gets into the swing of things,
it gets to be relatively routine.  THE ONLY MAJOR PROVISO TO
USABLE IN CLADISTICS.  Especially when using DELTA for writing
descriptions one ends up focussing on  what might be called
"differentiae" rather than on shared similarities.  One can modify
a DELTA list to use in cladistics, but using it directly leads to
some rather entertaining phylogenies.  Oh, by the way, I work on
polychaetes and I know that several ichthyologists are using the
techniques:  It is more widely used than suggested by the
comments so far.  Keep on scoring!!


[now, the above letter contrasts with next, somewhat, don't you


Dear Ingolf:

I saw your earlier message about DELTA and Entomologists, but did
not want to respond because my comments were basically negative.
Now that I've seen what others have said, I can tell you what I
think about DELTA.

I am currently developing computerized keys for the identification
of **********.  I am using DELTA primarily as an example of how not
to make interactive keys.  Because I am only making keys for
non-entomologists to use, I am only interested in INTKEY, and not
in any other features of DELTA.  The number of other programs out
there that do essentially the same thing as INTKEY indicates to me
that this is what everyone else is interested in also.

I also have a problem with the idea of making all my hard earned
knowledge available in an easily manipulated form that basically
obviates the need for ME to work any further on the organisms.  I
get the feeling that I'm computerizing myself right out of a

There are several problems with DELTA.

1.  It is not an expert system, which is really what I want in an
interactive key.
      [DELTA itself does not profess to be the expert system; INTKEY
      is the expert system software; other aspects of DELTA are used
      to generate and manage the data INTKEY runs on]

2.  I feel that the search algorithm is the opposite of what it
should be.  I would prefer a routine that separates the taxa with
unique characters FIRST. Instead, the program looks for characters
that have poor consistency and tend to show up in all taxonomic
groups.  This is really frustrating for a phylogeneticist.
      [Good taxonomic keys split sets of taxa into large, potentiall
      equal sets on each half of the dichotomous keys.  Keys that
      clip off taxa one at a time based on unique features are
      lousy, and get damned long, and generally don't work.  The key
      algorithm selects taxa as you weight them or predefine that
      they should be used, so you have a great deal of control over
      how the key is generated.  I don't see why this writer says
      that the program seeks characters of poor consistencey and
      which occur in all taxonomic groups.  That makes no sense to
      me, and isn't what occurs anyway, in my experience.]

3.  It is a DOS program.  Most academic types are more comfortable
with Macintosh.  Had the programs been originally written for the
Mac, which of course, could not have been done by low-powered
programmers, the software would now be wildly popular.
Furthermore, many of the interface problems would not have existed.
Perhaps a Windows version will make the programs work better.
      [I don't know about this "most academic types" idea - that's
      perhaps more like people around him are Mac users and
      therefore that's the majority; around me, most everyone is an
      IBM user, so it seems to me that's the norm...  PAUP 2.4.1 was
      originally written for IBM, by the way; HENNIG86! shall I go
      on?  Seems to me that there are a heck of a lot of IBM people
      out there.]
      [A windows version of INTKEY is due to be available soon, and
      I hope that this will improve the interface problems that this
      writer is talking about!]

4.  The interface really sucks.  It is not intuitive.  This is the
single most important aspect of any software today.  The command
line interface makes it a dinosaur.  There are too many things to
do to get to an answer.  The software does not guide the user
through each consecutive step.  It is not clear at any given point
what to do next.  You cannot view text and graphics at the same
time.  With all the really slick multimedia stuff out there these
days, I don't think DELTA has a chance of being adopted as a
standard for zoology.
      [I agree, and so do others I've talked to, that the interface
      sucks and that it is not intuitive.  No argument from me.  I
      think Mike should post his fulsome reply to this statement,
      for I'm still not sure that I buy it.  I'm assuming the
      windows version of INTKEY will solve the multimedia problems
      mentioned here.  The intuitive part is something that is a
      whole other ball of wax.]

5.  The people trying to write keys using DELTA are accustomed to
writing and using dichotomous keys.  For better or worse, the
program would be more popular if it could think like a taxonomist,
i.e., it WAS an expert system, and could flow through the data the
way I would.  The problem here, of course, is the search routine
(see #2 above).

6.  I do all my figures on a Mac (= super VGA).  Everything is fine
with DELTA as long as the computer you're using has a super VGA
card and driver.  If not, the figures, which are the only good part
of the entire key, will not work.  So much for that idiotic
argument that DOS and IBM XT/AT compatible PCs are some kind of
universal "standard."
      [Let's face it, Mac users think the IBM platform sucks the big
      one.  IBM users think that Mac users are just a bunch of lazy
      louts who haven't the aptitude to use a real computer.  I use
      both and think they have differing assets and there really
      ought not be this animosity.  Nor should we be hurling insults

7.  The data files, and to some extent, the directives files, are
too difficult to modify.  Let's face it.  The DELTA system is
really a programming language. Not a very complex or powerful one,
but a programming language nonetheless.  I think it is expecting a
lot of a taxonomist, who may have just gotten used to the idea of
typing a manuscript on his PC, to ask him to learn a programming
language.  You should be able to write the data and other program
files with the same ease that you should be able to use the
program.  The data files should be organized more intuitively and
input should be more automated.  Much like programming environments
for the Macintosh are done.
      [At this point things are degenerating. There is a pretty
      marked difference between the expectations that our competing
      platform camps have of software.  I should reiterate some
      comments that Mike Dallwitz has made to me, paraphrasing:
      basically, "if you want software that can do all the things
      you expect of it, it's bound to become complicated and a user
      has to be willing to spend a little time to learn it."  Let me
      add to this also, that there's a difference between DEVELOPING
      an expert system, and USING IT.  Those who develop a data base
      that INTKEY runs on, are the ones who have to learn all the
      ins and outs of DELTA, the intricacies of the data files and
      such.  I'm not saying this couldn't be set up a little more
      ituitively, just that those who make up data bases surely have
      to be prepared to understand the workings more than those who
      are going to use the system.  For example, why should those
      who buy the beetle larvae system have to know everything there
      is to know about DELTA?]

8.  As far as the data basing features of DELTA, I don't see
anybody having the time or money to go back and enter in all the
data on each species that they have already done.  There is also
the problem of cross-leveling all the data for each species which
means going back and looking at them again.  It is just too much
work to do whether it results in a pub or not.
      [No-one's expected to go back and redo his life's work; that's
      pretty much a given because it's not very time effective. Of
      course, it might be another story if there were some special
      value in it]

Well, I could go on and on about DELTA.  Give me call sometime if
you really want to get me started.  I hope that we can get some
money here to develop the kind of interactive keys that I think
most people would like to see.  I see the data basing of taxonomic
information as a separate issue, but maybe that will eventually
catch on also.



      I consider it an excellent tool for helping organize one's
data gathering and for INTERACTIVE identification.  Manuscripts
that I have seen that were written relying heavily on delta have
convinced me that it is not the way to go to prepare floristic
accounts - or only as step one one a long staircase.  Perhaps the
criticism should be that people tend to treat as it as step - 2 or
3.  The keys that I have seen have used relatively obscure
characters; some did not allow for all the variation in the
description (which surprised me).  After reading a number of
strictly parallel descriptions, I have reached the conclusion that
they can easily conceal the significant information in a deluge of
unhelpful information.  The wording achieved with Delta is also
often very awkward [but the most recent release has significant
improvements in this area; besides, you can really develop your
character set to adjust these oddities].  As a means of providing
an initial draft, or a reference work, fine.  For a final product,
not without more work than is generally used.  And I suspect less
work is involved if one starts hand work from the first delta
      Why do I not use it myself? Too impatient. Then again, it
might improve the quality of my work... I think people are not
always prepared to admit how much basic taxonomic work needs to be
done before one starts using DELTA to write a revision.  I have no
particular quarrel with using it as a teaching device.  I do not do
so, it is difficult enough getting the material I consider
essential across.  As you may gather, I reached the decision that
DELTA would not be a more efficient way of achieving my goals for
the course.

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