1 /* -*- mode: C++; indent-tabs-mode: nil; -*-
3 * This file is a part of LEMON, a generic C++ optimization library.
5 * Copyright (C) 2003-2009
6 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
7 * (Egervary Research Group on Combinatorial Optimization, EGRES).
9 * Permission to use, modify and distribute this software is granted
10 * provided that this copyright notice appears in all copies. For
11 * precise terms see the accompanying LICENSE file.
13 * This software is provided "AS IS" with no warranty of any kind,
14 * express or implied, and with no claim as to its suitability for any
24 \page lgf-format LEMON Graph Format (LGF)
26 The \e LGF is a <em>column oriented</em>
27 file format for storing graphs and associated data like
30 Each line with \c '#' first non-whitespace
31 character is considered as a comment line.
33 Otherwise the file consists of sections starting with
34 a header line. The header lines starts with an \c '@' character followed by the
35 type of section. The standard section types are \c \@nodes, \c
37 and \@attributes. Each header line may also have an optional
38 \e name, which can be use to distinguish the sections of the same
41 The standard sections are column oriented, each line consists of
42 <em>token</em>s separated by whitespaces. A token can be \e plain or
43 \e quoted. A plain token is just a sequence of non-whitespace characters,
44 while a quoted token is a
45 character sequence surrounded by double quotes, and it can also
46 contain whitespaces and escape sequences.
48 The \c \@nodes section describes a set of nodes and associated
49 maps. The first is a header line, its columns are the names of the
50 maps appearing in the following lines.
51 One of the maps must be called \c
52 "label", which plays special role in the file.
54 non-empty lines until the next section describes nodes of the
55 graph. Each line contains the values of the node maps
56 associated to the current node.
60 label coordinates size title
61 1 (10,20) 10 "First node"
62 2 (80,80) 8 "Second node"
63 3 (40,10) 10 "Third node"
66 The \c \@arcs section is very similar to the \c \@nodes section, it
67 again starts with a header line describing the names of the maps, but
68 the \c "label" map is not obligatory here. The following lines
69 describe the arcs. The first two tokens of each line are the source
70 and the target node of the arc, respectively, then come the map
71 values. The source and target tokens must be node labels.
81 If there is no map in the \c \@arcs section at all, then it must be
82 indicated by a sole '-' sign in the first line.
92 The \c \@edges is just a synonym of \c \@arcs. The \@arcs section can
93 also store the edge set of an undirected graph. In such case there is
94 a conventional method for store arc maps in the file, if two columns
95 have the same caption with \c '+' and \c '-' prefix, then these columns
96 can be regarded as the values of an arc map.
98 The \c \@attributes section contains key-value pairs, each line
99 consists of two tokens, an attribute name, and then an attribute
100 value. The value of the attribute could be also a label value of a
101 node or an edge, or even an edge label prefixed with \c '+' or \c '-',
102 which regards to the forward or backward directed arc of the
109 caption "LEMON test digraph"
112 The \e LGF can contain extra sections, but there is no restriction on
113 the format of such sections.
118 // LocalWords: whitespace whitespaces