Graph Modelling Language

Graph Modeling Language is a hierarchical ASCII-based file format for describing graphs. It has been also named Graph Meta Language.

Example

A simple graph in GML format:


graph 
 node 
 node 
 edge 
 edge 
 edge

Cytoscape, an open source bioinformatics software platform for visualizing molecular interaction networks, loads and save previously-constructed interaction networks in GML.
igraph, an open source network analysis library with interfaces to multiple programming languages.
Gephi, an open source graph visualization and manipulation software.
Graph-tool, a free Python module for manipulation and statistical analysis of graphs.
NetworkX, an open source Python library for studying complex graphs.
Tulip (software) is a free software in the domain of information visualisation capable of manipulating huge graphs.
yEd, a free Java-based graph editor, supports import from and export to GML.
The Graphviz project includes two command-line tools that can convert to and from the DOT file format.
Wolfram Language, a general very high-level programming language, supports .