Graphviz is a set of graph drawing tools from AT&T Research and Lucent Bell
Laboratories.

It includes:
- dot: makes hierarchical layouts of directed graphs 
- neato: makes "spring" model layouts of undirected graphs 
- lefty: a programmable graphics editor
- dotty: a customizable interface written in LEFTY 
- tcldot: a customizable graphical interface written in TCL
- libgraph: the base library for graph tools 
- various associated utilities
