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
- tcldot: a customizable graphical interface written in TCL
  (part of "tcl" option)
- libcgraph: the base library for graph tools
- various associated utilities