I used the code below to create a graphic using dot (graphviz).
digraph
{
node [color=Blue,shape=box]
1.1 [label=\"Frequency of t exceeds upper threshold\"]
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.