Text wrapping with dot (graphviz)

graphviz doesn't support automatic line breaks. You have to put the \n in manually.

you can set a width and a height to a node and define it as fixedsized - this will limit the size of the node and draw only as much text as fits into the node

Although graphviz does not support text wrapping by itself, dot2tex (latex+graphviz) does. The dot2texi latex package gives an all-in-one solution, with (from the users point of view) a single call to a single tool to build the graph.

A short example:

\documentclass{standalone}
\usepackage{dot2texi}
\usepackage{tikz}
\usetikzlibrary{shapes,arrows}
\begin{document}
\begin{dot2tex}[dot]
digraph G {                                             
d2toptions ="--autosize"
node    [lblstyle="text width=10em,align=center"]
a       [texlbl="This text will be automatically wrapped, for example at a fixed width."]
b       [texlbl="Manual linebreaks from past century can be avoided!"]
a -> b
}
\end{dot2tex}                                               
\end{document}

This can be compiled invoking for example: pdflatex --shell-escape myFile.tex, the text will be automatically wrapped at the prescribed fixed width.

As a side note, this tool seems a handy workaround for graphviz' limited typesetting control of the nodes contents.