File format
DOT is a graph description language, developed as a part of the Graphviz project. DOT graphs are typically stored as files with the codice_1 or codice_2 filename extension — codice_1 is preferred, to avoid confusion with the codice_2 extension used by versions of Microsoft Word before 2007. codice_5 is also the name of the main program to process DOT files in the Graphviz package.
Various programs can process DOT files. Some, such as "dot", "neato", "twopi", "circo", "fdp", and "sfdp", can read a DOT file and render it in graphical form. Others, such as "gvpr", "gc", "acyclic", "ccomps", "sccmap", and "tred", read DOT files and perform calculations on the represented graph. Finally, others, such as "lefty", "dotty", and "grappa", provide an interactive interface. The GVedit tool combines a text editor and a non-interactive viewer. Most programs are part of the Graphviz package or use it internally.
DOT is historically an acronym for "DAG of tomorrow", as the successor to a DAG format and a "dag" program which handled only directed acyclic graphs.
Syntax.
Graph types.
Undirected graphs.
At its simplest, DOT can be used to describe an undirected graph. An undirected graph shows simple relations between objects, such as reciprocal friendship between people. The codice_6 keyword is used to begin a new graph, and nodes are described within curly braces. A double-hyphen (codice_7) is used to show relations between the nodes.
// The graph name and the semicolons are optional
graph graphname {
 a -- b -- c;
 b -- d;
Directed graphs.
Similar to undirected graphs, DOT can describe directed graphs, such as flowcharts and dependency trees. The syntax is the same as for undirected graphs, except the codice_8 keyword is used to begin the graph, and an arrow (- ;) is used to show relationships between nodes.
digraph graphname {
 a - ; b - ; c;
 b - ; d;
Attributes.
Various attributes can be applied to graphs, nodes and edges in DOT files. These attributes can control aspects such as color, shape, and line styles. For nodes and edges, one or more attribute–value pairs are placed in square brackets codice_9 after a statement and before the semicolon (which is optional). Graph attributes are specified as direct attribute–value pairs under the graph element, where multiple attributes are separated by a comma or using multiple sets of square brackets, while node attributes are placed after a statement containing only the name of the node, but not the relations between the dots.
graph graphname {
 // This attribute applies to the graph itself
 size="1,1";
 // The label attribute can be used to change the label of a node
 a [label="Foo"];
 // Here, the node shape is changed.
 b [shape=box];
 // These edges both have different line properties
 a -- b -- c [color=blue];
 b -- d [style=dotted];
 // [style=invis] hides a node.
HTML-like labels are supported, although initially Graphviz did not handle them.
Comments.
DOT supports C and C++ style single line and multiple line comments. In addition, it ignores lines with a number sign symbol codice_10 as their first character, like many interpreted languages.
Layout programs.
The DOT language defines a graph, but does not provide facilities for rendering the graph. There are several programs that can be used to render, view, and manipulate graphs in the DOT language:
Notes.
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