Graph Modeling Language (GML) is a hierarchical ASCII-based file format for describing graphs. It has been also named Graph Meta Language.
A simple graph in GML format:
graph [ comment "This is a sample graph" directed 1 id n42 label "Hello, I am a graph" node [ id 1 label "node 1" thisIsASampleAttribute 42 ] node [ id 2 label "node 2" thisIsASampleAttribute 43 ] node [ id 3 label "node 3" thisIsASampleAttribute 44 ] edge [ source 1 target 2 label "Edge from node 1 to node 2" ] edge [ source 2 target 3 label "Edge from node 2 to node 3" ] edge [ source 3 target 1 label "Edge from node 3 to node 1" ]]
Apache Tinkerpop, an open source graph computing framework.Clairlib, a suite of open-source Perl modules intended to simplify a number of generic tasks in natural language processing (NLP), information retrieval (IR), and network analysis (NA).Cytoscape, an open source bioinformatics software platform for visualizing molecular interaction networks, loads and save previously-constructed interaction networks in GML.Gephi, an open source graph visualization and manipulation software.Graph-tool, a free and efficient Python module for manipulation and statistical analysis of graphs.igraph, an open source library for the analysis of complex networks, with higher level interfaces for R, Python and Ruby.NetworkX, an open source Python library for studying complex graphs.ocamlgraph, a graph library for OCaml.OGDF, the Open Graph Drawing Framework, an open source C++ library containing implementations of various graph drawing algorithms. The library is self-contained; optionally, additional packages like LP-solvers are required for some implementations.Tulip (software) is a free software in the domain of information visualisation capable of manipulating huge graphs (with more than 1.000.000 elements).yEd, a free Java-based graph editor, supports import from and export to GML.Social Network Visualizer, a free and open-source, user-friendly application for social network analysis and visualization developed in C++ and Qt.