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Free DELTA

An Open Source System for Processing Taxonomic Descriptions

About DELTA

DELTA stands for DEscription Language for TAxonomy. The DELTA system consists of a flexible format for coding descriptive taxonomic information and a set of associated programs which manipulate the data to produce natural-language descriptions and keys, interactive identification and information retrieval, and to convert data into formats required by programs for phenetic and cladistic analysis.

The DELTA format allows all kinds of characters, both qualitative (binary or multistate, ordered or unordered) or quantitative (integer or real, with units if needed). Comments are allowed anywhere, and character dependency can be described. Directives are used to control computer processing of DELTA-coded data.

The original DELTA system has been under development since the mid 1970's by Mike Dallwitz at CSIRO Division of Entomology, Canberra, Australia. Later on, similar packages for processing of DELTA data were developed in the United Kingdom by Richard Pankhurst of the Royal Botanic Gardens at Edinburgh (PANKEY), in The Netherlands by Eric Gouda at the Botanic Gardens of Utrecht University (TAXASOFT), in Australia by Nicholas Lander at the Western Australian Herbarium (DMSWIN), in Spain by Antonio Valdecasas at the Museo Nacional de Ciencias Naturales (EDEL), in Germany by Gregor Hagedorn at the Institute of Microbiology, Federal Biological Research Center (DELTAAccess), in the United States by Michael Bartley and Noel Cross at the Arnold Arboretum of the Harvard University (NaviKey), in Italy by Claudio Rivetti and Riccardo Percudani at University of Parma (WebDelta), and in Brazil by Mauro J. Cavalcanti at Museu Nacional/Universidade Federal do Rio de Janeiro (DIANA), among several other DELTA programs.

In 1988, DELTA was adopted by the International Working Group on Taxonomic Databases for Plant Sciences (TDWG) as an internationally recognised standard for data encoding and exchange. Combining traditional taxonomic practices with modern information technology, the DELTA system has since became one of the most valuable and widely used computerized tools for biodiversity research.

Many datasets have already been prepared with DELTA, for flowering plant families, grasses, sedges, legumes, beetles (adults and larvae), ants, corals, plant viruses, etc. Several of these datasets incorporate line, gray-scale and color illustrations, and some are freely available on the Internet (at the time of writing, there are 68 datasets in the DELTA website and 22 datasets in the NaviKey website).

About Free DELTA back to top

The Free DELTA project was launched in April, 2000 with the aim of creating a complete cross-platform, free, open source software system for processing taxonomic descriptions coded in DELTA format, following the decision by CSIRO Division of Entomology to stop funding the development of the original DELTA programs.

In May, 2005 the Free DELTA project was registered at SourceForge, the world's largest open source software development website, with the largest repository of open source code and applications available on the Internet, and where the Free DELTA Web site is now to be located on a permanent basis.

To begin with, the Free DELTA package includes a library for parsing DELTA-format files plus all the utilities needed to process taxonomic data coded in DELTA: format-conversion, key-construction, distance-matrix generation, and interactive identification programs, as well as a specialized editor for handling taxonomic descriptive data. We hope to supply, eventually, everything that normally comes with the DELTA system, and anything else useful, including on-line documentation.

The Free DELTA parser libraries provides a standard, versatile and extensible collection of routines for handling DELTA datasets. This set of routines is available as Python, C++, and Object Pascal libraries and provide the basic support for the Free DELTA software; furthermore, they are ready for incorporation within individual application programs or database systems as they are created by different software developers. These routines are released as complete, open source code. So, a user who needs a different system for taxonomic data management is able to develop it himself, or hire any available programmer or company to develop it for him or her, while retaining the benefits of a standard format for encoding taxonomic data. The availability of full source code also enables a user to tailor these routines according to his or her more specific needs. It is hoped that this will help to further expand the DELTA user community, as well as to strengthen the role of DELTA as a standard taxonomic data coding and transfer system.

On the other side, Free DELTA programs will be able to process regular DELTA-coded files, but will not be identical to the original DELTA system. We will make all improvements that are convenient, based on our experience with other taxonomic computing systems. In particular, it will have a better treatment of quantitative data, more analytical and format-conversion procedures, and many other things.

All Free DELTA software is released as free software, under the GNU General Public License.

Free DELTA New Generation back to top

In July, 2008 the Free DELTA NG ("New Generation") Initiative has been launched to promote the development and sharing of free, open source DELTA software tools entirely based on open source. The Free DELTA NG Initiative also defined the conditions that a given software tool should meet in order to be considered as a Free DELTA program (see below).

Components back to top

Downloads back to top

Notice: The Free DELTA distribution files come in either .tar.gz or .zip format. The .tar.gz format is most suitable for UNIX machines (including GNU/Linux) and the .zip format is most suitable for DOS/Windows PCs.

Support back to top

We recommend to join the DELTA-L mailing list for up-to-date information and efficient support.

Free DELTA Contributors back to top

Mauro J. Cavalcanti
Zoologist and information scientist, conceived the Free DELTA Project in April, 2000, maintains this website, implemented the original version of the PyDELTA library and manages the DELTA NG Initiative.
Eric Zucher
Software developer. Implemented and maintains the "classic" DELTA programs in GFORTRAN.
Thomas Kluyver
Botanist and computer programmer. Implemented and maintains substantial modifications of the PyDELTA library.
Craig Robbins
Botanist and computer programmer. Implemented and maintains the DeltaQt library. 
Denis Ziegler
Computer programmer and amateur botanist. Implemented the Free DELTA library of C++ routines for reading files in DELTA format.
Guillaume Rousse
Biologist and software developer. Implemented patches to the Free DELTA library of C++ routines. 
Bastiaan Wakkie
Software developer and amateur entomologist. Implemented patches to the Free DELTA library of C++ routines.

How To Contribute back to top

Able, committed software developers and biologists are always welcome in the Free DELTA project.

Individual programmers can contribute by writing a compatible duplicate of some DELTA utility and giving it to the Free DELTA project. We are looking for people for whom knowing they are helping humanity (by assuring the continuity and free availability of DELTA as a valuable biodiversity information management tool) is more important than money.

To qualify for Free DELTA, a software is expected to conform to the conditions below:

Related Projects back to top

Other free, open source taxonomic computing projects:

Based on the DELTA format:

Not based on the DELTA format:

Acknowledgments back to top

We are grateful to everybody who has helped us by contributing knowledge, good ideas, moral support, programming time, technical expertise, and bug reports. We are particularly indebted (in alphabetical order) to Adriano Kury, Adrian Pinder, Alex Cherepanov, Chuck Cannon, Craig Robbins, Doug Ashton, Edinaldo Nelson, Eric Gouda, Eric Zurcher, Frank Tolstrup, George (Buz) Wilson, Gregor Hagedorn, Jeffrey Shaw, Joe Kirkbride, Kehan Harman, Matt Buys, Mike Dallwitz, Nicolas Degallier, Peter Roopnarine, Susan Farmer, Thomas Kluyver, Winston Ponder. Thank you very much!


Send inquiries & questions to Mauro J. Cavalcanti.

Copyright © 2000-2014 The Free DELTA Project.

Verbatim copying and distribution is permitted in any medium, provided this notice is preserved.


Last updated April 28, 2014