Leibniz Laboratory, The Graph Theory Team

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Our software

Cabri-graph

The object of this software is to handle graphs (edition, operations, computations).

Cabri-graph was the first product conceived and developed in the former Laboratory for Discrete Structures and Didactics (LSD2) of our Institute, in the framework of the national "Cabri" project.
The platform on which it was, and still is, developed is the Macintosh. Cabri-graph is a freeware tool in perpetual development and maintenance. It is available on the CabriGraph site. A brief history of Cabri-graph can also be consulted.

Cabri-Clutter

This software, conceived by Claude Benzaken, caters to the study of those Sperner hypergraphs (also known as Clutters) that are bicritical for the chromatic number. This means that the clutter has no isolated vertex and that, for every edge of the clutter, the clutter formed by those edges that do not meet this edge has chromatic number two less than the original clutter. On the origin and the mathematical aspects of this concept you can consult the project of a long article by Claude Benzaken: "From logical Gates Synthesis to Bicritical Clutters".
Mathematically, the bicritical clutters of chromatic number 2 or 3 are perfectly known. The software in this first version gives all elements to attack the bicritical clutters with chromatic number 4.
Beyond the specific concern of the software, a great number of general, basic procedures (editing, display, operations and computation) can be used on other purposes and be intersting to a broader range of users. Cabri-Clutter works on Macintosh and in two platforms (680x0 and PowerPC). It is freeware and can be downloaded from the Clutter site.

Cabri-Boolean

A clutter may be viewed as a positive Boolean formula (i.e. without negation). Enlarging slightly the data type, it was possible to produce a more general software program, devoted not specially to some specific goal but simply to handle any Boolean normal form (disjunctive or conjunctive).This Boolean software, in continuation with Clutter, was designed in August 1997 by C. Benzaken.
This software enables us to edit any normal forms (manually, randomly, or given by linear inequalities with integer coefficients). From any given form, it builds any other equivalent form according to selected criteria. The dualization plays a major part in all the procedures. At last, it implements some recognition algorithms with respect to well-known classes of formulas (Horn formulas , disguised or not, quadratic, regular, and so on..) where dualization or the satisfiability problem has a polynomial complexity.
This software works for MacIntosh only and in two platforms (680x0 and PowerPC). It is freeware and can be downloaded from the CabriBoolean site.