graphviz

About graphviz

From Debian's package description

Graph drawing addresses the problem of visualizing structural information by constructing geometric representations of abstract graphs and networks. Automatic generation of graph drawings has important applications in key technologies such as database design, software engineering, VLSI and network design and visual interfaces in other domains. Situations where these tools might be particularly useful include:

• you would like to restructure a program and first need to understand the relationships between its types, procedures, and source files
• you need to find the bottlenecks in an Internet backbone - not only individual links, but their relationships
• you're debugging a protocol or microarchitecture represented as a finite state machine and need to figure out how a certain error state arises
• you would like to browse a database schema, knowledge base, or distributed program represented graphically
• you would like to see an overview of a collection of linked documents
• you would like to discover patterns and communities of interest in a database of telephone calls or e-mail messages

This package contains the command-line tools.

From Debian's description of the graphviz package, under that package's license.