Ordered Graph Data Language
"OGDL is a textual format that represents trees or graphs of data, where the nodes are strings and the edges are space or indentation. Its main objectives are simplicity and readability.
The text format specified here represents a directed graph G=(N,E), where N is an ordered bag of nodes and E a relation NxN. Nodes are represented by strings. Each member of E is an arc (edge), and is represented by space between nodes"
(this example makes more sense if you look at the example page: http://ogdl.sourceforge.net/examples.htm)