Native File Format for Graphs
The native file format for graphs consists of several lines which are
separated by endl . Commentlines have a # character
in the first column and are ignored. The output can be partitioned in
three sections:
Header Section
The first line always contains the string LEDA.GRAPH . If
the graph type is not parameterized, i.e. graph,
the following two lines both contain the string void . In
case the graph is parameterized, i.e. GRAPH ,
these lines contain a description of the node type and the edge type. The fourth
line specifies if the graph is either directed (1) or undirected (2).
Nodes Section
The first line contains n , the number of nodes in the graph.
The nodes are ordered and numbered according to their position in the
node list of the graph. Each of the following n lines contains
the information which is associated with the respective node of the graph.
When the information of a node (or an edge) is sent to an output stream,
it is always enclosed by the strings { and } .
If the graph is not parameterized, then the string between these parantheses
is empty, so that all the n lines contain the string {} .
Edges Section
The first line contains m , the number of edges in the graph.
The edges of the graph are ordered by two criteria: first according to
the number of their source node and second according to their position
in the adjacency list of the source node. Each of the next m
lines contains the description of an edge which consists of four spaceseparated
parts:
 the number of the source node
 the number of the target node
 the number of the reversal edge or 0, if no such edge is set
 the information associated with the edge (cf. nodes section)
Note: For the data type planar_map
the order of the edges is important, because the ordering of the edges
in the adjacency list of a node corresponds to the counterclockwise ordering
of these edges around the node in the planar embedding. And the information
about reversal edges is also vital for this data type.
Example of a Graph
The following lines show a graph in native file format. It consists of
five nodes and seven edges. The nodes have a parameter of type string
and the edges have a parameter of type int.
#header section
LEDA.GRAPH
string
int
1
#nodes section
5
{v1}
{v2}
{v3}
{v4}
{v5}
#edges section
7
1 2 0 {4}
1 3 0 {3}
2 3 0 {2}
3 4 0 {3}
3 5 0 {7}
4 5 0 {6}
5 1 0 {1}
Example of how to
use GML format and native graph file format
Strength
Disadvantage
Tips
 Use the native format if you need to store a LEDA graph or GraphWin
