--- /dev/null
+\documentclass[11pt]{article}
+\usepackage{graphicx}
+\usepackage{times}
+\pagestyle{myheadings}
+\author{Emden Gansner and Eleftherios Koutsofios and Stephen North}
+\def\dot{{\it dot}}
+\def\dag{{\it dag}}
+\def\DOT{{\it DOT}}
+\newcommand{\lastedited}{October 7, 2009}
+\date{\lastedited}
+\newcommand{\mymark}{{\it dot} User's Manual, \lastedited \hfil }
+\markboth{\mymark}{\mymark}
+\begin{document}
+\bibliographystyle{alpha}
+\title{Drawing graphs with \dot}
+\maketitle
+\begin{abstract}
+\noindent
+{\dot} draws directed graphs as hierarchies.
+It runs as a command line program, web visualization
+service, or with a compatible graphical interface.
+Its features include well-tuned layout algorithms
+for placing nodes and edge splines, edge labels,
+``record'' shapes with ``ports'' for drawing data structures;
+cluster layouts; and an underlying file language for
+stream-oriented graph tools.
+Below is a reduced module dependency graph of an SML-NJ compiler
+that took 0.23 seconds of user time on a 3 GHz Intel Xeon.
+
+\vspace*{.25in}
+\centerline{
+ \includegraphics[width=4.0in]{smlred}
+}
+\end{abstract}
+
+\newpage
+\section{Basic Graph Drawing}
+
+\if 0
+{\bf The attributes z and quantum are not described, though they
+appear in the tables. The original document describes the edge id
+attribute. As far as I can tell, this isn't implemented.
+All details are here and up-to-date.
+The question is which, if any, should be removed,
+and should the document structure be changed. Some of the
+appendices might belong in the main body, and parts of the main
+body (e.g., the attribute tables and command line information)
+might be better in the appendix. Maybe the Node and Edge Placement
+section should appear before Drawing Size and Spacing.
+The figures should probably be regenerated using dot, and we might
+want to redo the timing for the abstract figure.}
+\fi
+
+\dot\ draws directed graphs. It reads attributed graph text files and
+writes drawings, either as graph files or in a graphics format
+such as GIF, PNG, SVG, PDF, or PostScript (which can also be converted
+to PDF with some additional features not in the native PDF driver).
+
+\dot\ draws graphs in four main phases.
+Knowing this helps you to understand what kind of
+layouts \dot\ makes and how you can control them.
+The layout procedure used by \dot\ relies on the graph
+being acyclic. Thus, the first step is to break any
+cycles which occur in the input graph by reversing
+the internal direction of certain cyclic edges.
+The next step assigns nodes to discrete ranks or levels.
+In a top-to-bottom drawing, ranks determine $Y$ coordinates.
+Edges that span more than one rank are broken into chains
+of ``virtual'' nodes and unit-length edges.
+The third step orders nodes within ranks to avoid crossings.
+The fourth step sets $X$ coordinates of nodes to keep edges short,
+and the final step routes edge splines.
+This is the same general approach as most hierarchical graph drawing
+programs, based on the work of Warfield \cite{warfield},
+Carpano \cite{carpano} and Sugiyama \cite{stt}.
+We refer the reader to \cite{gknv:methods}
+for a thorough explanation of \dot's algorithms.
+
+\dot\ accepts input in the \DOT\ language (cf. Appendix~\ref{grammar}).
+This language describes three main kinds of objects:
+graphs, nodes, and edges.
+The main (outermost) graph can be directed
+({\tt digraph}) or undirected {\tt graph}.
+Because \dot\ makes layouts of directed graphs,
+all the following examples use {\tt digraph}.
+(A separate layout utility, {\it neato},
+draws undirected graphs \cite{neatoguide}.)
+Within a main graph, a {\tt subgraph} defines a
+subset of nodes and edges.
+
+Figure~\ref{fig:graph1} is an example graph in the \DOT\ language.
+Line 1 gives the graph name and type.
+The lines that follow create nodes, edges, or subgraphs,
+and set attributes. Names of all these objects may be
+C identifiers, numbers, or quoted C strings.
+Quotes protect punctuation and white space.
+
+\begin{figure}[p]
+\begin{verbatim}
+1: digraph G {
+2: main -> parse -> execute;
+3: main -> init;
+4: main -> cleanup;
+5: execute -> make_string;
+6: execute -> printf
+7: init -> make_string;
+8: main -> printf;
+9: execute -> compare;
+10: }
+\end{verbatim}
+\caption{Small graph}
+\label{fig:graph1}
+\end{figure}
+
+\begin{figure}[p]
+ \centerline {
+ \includegraphics[width=3.0in]{graph1}
+ }
+ \caption{Drawing of small graph}
+ \label{fig:drawing1}
+\end{figure}
+
+A node is created when its name first appears in the file.
+An edge is created when nodes are joined by the edge operator \verb"->".
+In the example, line 2 makes edges from {\it main} to {\it parse},
+and from {\it parse} to {\it execute}.
+Running \dot\ on this file (call it \verb"graph1.dot")
+\begin{verbatim}
+ $ dot -Tps graph1.dot -o graph1.ps
+\end{verbatim}
+yields the drawing of Figure~\ref{fig:drawing1}.
+The command line option \verb"-Tps" selects PostScript (EPSF) output.
+\verb"graph1.ps" may be printed, displayed by a PostScript viewer,
+or embedded in another document.
+
+It is often useful to adjust the representation or placement of nodes
+and edges in the layout. This is done by setting attributes of nodes,
+edges, or subgraphs in the input file.
+Attributes are name-value pairs of character strings.
+Figures~\ref{fig:graph2} and \ref{fig:drawing2} illustrate
+some layout attributes. In the listing of Figure~\ref{fig:graph2},
+line 2 sets the graph's {\tt size} to {\tt 4,4}
+(in inches).\footnote{Generally, input dimensions are in inches;
+output is in 1/72s of an inch, equal to one {\it point} in Postscript.
+You can override the default input scaling with the \verb"-s" command argument,
+typically, \verb"-s 72" to scale the input in points. We know it is bad
+to have different input and output scales as well as not to have some
+way to specify units explicitly and we plan to correct that.}
+This attribute controls the size of the drawing; if the drawing is
+too large, it is scaled as necessary to fit.
+
+Node or edge attributes are set off in square brackets.
+In line 3, the node \verb"main" is assigned shape \verb"box".
+The edge in line 4 is straightened by increasing its
+\verb"weight" (the default is \verb"1").
+The edge in line 6 is drawn as a dotted line.
+Line 8 makes edges from {\tt execute} to {\tt make\_string} and {\tt printf}.
+In line 10 the default edge color is set to \verb"red".
+This affects any edges created after this point in the file.
+Line 11 makes a bold edge labeled {\tt 100 times}.
+In line 12, node \verb"make_string" is given a multi-line label.
+Line 13 changes the default node to be a box filled with a shade of blue.
+The node {\tt compare} inherits these values.
+
+\begin{figure}[p]
+\begin{verbatim}
+1: digraph G {
+2: size ="4,4";
+3: main [shape=box]; /* this is a comment */
+4: main -> parse [weight=8];
+5: parse -> execute;
+6: main -> init [style=dotted];
+7: main -> cleanup;
+8: execute -> { make_string; printf}
+9: init -> make_string;
+10: edge [color=red]; // so is this
+11: main -> printf [style=bold,label="100 times"];
+12: make_string [label="make a\nstring"];
+13: node [shape=box,style=filled,color=".7 .3 1.0"];
+14: execute -> compare;
+15: }
+\end{verbatim}
+\caption{Fancy graph}
+\label{fig:graph2}
+\end{figure}
+
+\begin{figure}[p]
+ \centerline {
+ \includegraphics[width=2.5in]{graph2}
+ }
+ \caption{Drawing of fancy graph}
+ \label{fig:drawing2}
+\end{figure}
+
+\section{Drawing Attributes}
+
+The complete list of attributes that affect graph drawing
+is summarized in Tables~\ref{tab:nattr}, \ref{tab:eattr} and \ref{tab:gattr}.
+
+\subsection{Node Shapes}
+\label{sect:shape}
+
+Nodes are drawn, by default, with {\tt shape=ellipse}, {\tt width=.75},
+{\tt height=.5} and labeled by the node name.
+Other common shapes include {\tt box}, {\tt circle}, {\tt record}
+and {\tt plaintext}.
+A complete list of node shapes is given in Appendix~\ref{app:shapes}.
+The node shape {\tt plaintext} is of particularly interest in
+that it draws a node without any outline, an important convention
+in some kinds of diagrams. In cases where the graph structure is of
+main concern, and especially when the graph is moderately large, the
+{\tt point} shape reduces nodes to display minimal content.
+When drawn, a node's actual size is the greater of the requested
+size and the area needed for its text label, unless {\tt fixedsize=true},
+in which case the {\tt width} and {\tt height} values are enforced.
+
+Node shapes fall into two broad categories: polygon-based and
+record-based.\footnote{There is a way to implement custom node shapes,
+using {\tt shape=epsf} and the {\tt shapefile} attribute, and
+relying on PostScript output.
+The details are beyond the scope of this user's guide.
+Please contact the authors for further information.} All node
+shapes except {\tt record} and {\tt Mrecord} are considered polygonal,
+and are modeled by the number of sides (ellipses and circles being
+special cases), and a few other geometric properties. Some of these
+properties can be specified in a graph. If {\tt regular=true}, the
+node is forced to be regular. The parameter {\tt peripheries} sets
+the number of boundary curves drawn. For example, a doublecircle
+has {\tt peripheries=2}.
+The {\tt orientation} attribute specifies a clockwise rotation of the
+polygon, measured in degrees.
+
+The shape {\tt polygon} exposes all the polygonal parameters, and
+is useful for creating many shapes that are not predefined.
+In addition to the parameters {\tt regular}, {\tt peripheries} and
+{\tt orientation}, mentioned above, polygons are parameterized by
+number of sides {\tt sides}, {\tt skew} and {\tt distortion}.
+{\tt skew} is a floating point number (usually between $-1.0$ and $1.0$)
+that distorts the shape by slanting it from top-to-bottom,
+with positive values moving the top of the polygon to the right.
+Thus, {\tt skew} can be used to turn a box into a parallelogram.
+{\tt distortion} shrinks the polygon from top-to-bottom, with negative
+values causing the bottom to be larger than the top. {\tt distortion}
+turns a box into a trapezoid. A variety of these polygonal attributes
+are illustrated in Figures~\ref{fig:polygons} and~\ref{fig:polylist}.
+
+\begin{figure}[p]\footnotesize
+\begin{verbatim}
+1: digraph G {
+2: a -> b -> c;
+3: b -> d;
+4: a [shape=polygon,sides=5,peripheries=3,color=lightblue,style=filled];
+5: c [shape=polygon,sides=4,skew=.4,label="hello world"]
+6: d [shape=invtriangle];
+7: e [shape=polygon,sides=4,distortion=.7];
+8: }
+\end{verbatim}
+\caption{Graph with polygonal shapes}
+\label{fig:polylist}
+\end{figure}
+\begin{figure}[p]
+ \centerline {
+ \includegraphics{poly}
+ }
+ \caption{Drawing of polygonal node shapes}
+ \label{fig:polygons}
+ \vspace*{.5in} % tweak to make this figure use rest of page
+\end{figure}
+
+Record-based nodes form the other class of node shapes.
+These include the
+shapes {\tt record} and {\tt Mrecord}. The two are identical
+except that the latter has rounded corners. These nodes represent
+recursive lists of fields, which are drawn as alternating horizontal
+and vertical rows of boxes. The recursive structure is determined by
+the node's {\tt label}, which has the following schema: \\
+\begin{table}[h]
+\begin{tabular}{lll}
+{\it rlabel} & $\rightarrow$ & {\it field} ( '$|$' {\it field} )* \\
+{\it field} & $\rightarrow$ & {\it boxLabel} $|$ '{' {\it rlabel} '}' \\
+{\it boxLabel} & $\rightarrow$ & [ '$<$' {\it string} '$>$' ] [ {\it string} ] \\
+\end{tabular}
+\end{table}
+
+Literal braces, vertical bars and angle brackets must be escaped.
+Spaces are interpreted as separators between tokens, so they
+must be escaped if they are to appear literally in the text.
+The first string in a {\it boxLabel} gives a name to the field,
+and serves as a port name for the box (cf. Section~\ref{sect:ports}).
+The second string is used as a label for the field;
+it may contain the same escape sequences as multi-line
+labels (cf. Section~\ref{sect:labels}.
+The example of Figures~\ref{fig:record} and \ref{fig:recorddrawing}
+illustrates the use and some properties of records.
+
+\begin{figure}[p]\footnotesize
+\begin{verbatim}
+1: digraph structs {
+2: node [shape=record];
+3: struct1 [shape=record,label="<f0> left|<f1> mid\ dle|<f2> right"];
+4: struct2 [shape=record,label="<f0> one|<f1> two"];
+5: struct3 [shape=record,label="hello\nworld |{ b |{c|<here> d|e}| f}| g | h"];
+6: struct1 -> struct2;
+7: struct1 -> struct3;
+8: }
+\end{verbatim}
+\caption{Records with nested fields}
+\label{fig:record}
+\end{figure}
+\begin{figure}[p]
+ \centerline {
+ \includegraphics{recordex}
+ }
+ \caption{Drawing of records}
+ \label{fig:recorddrawing}
+\end{figure}
+
+\subsection{Labels}
+\label{sect:labels}
+
+As mentioned above, the default node label is its name.
+Edges are unlabeled by default.
+Node and edge labels can be set explicitly using the {\tt label}
+attribute as shown in
+Figure~\ref{fig:drawing2}.
+
+Though it may be convenient to label nodes by name, at other times
+labels must be set explicitly. For example, in drawing a file
+directory tree, one might have several directories named {\tt src},
+but each one must have a unique node identifier.
+The inode number or full path name are suitable unique identifiers.
+Then the label of each node can be set to the file name within
+its directory.
+
+Multi-line labels can be created by using the escape
+sequences \verb"\n", \verb"\l", \verb"\r" to terminate
+lines that are centered, or left or right justified.\footnote{The escape
+sequence $\backslash$N is an internal symbol for node names.}
+
+%The node shape {\tt Mdiamond}, {\tt Msquare} and {\tt Mcircle}
+%use the attributes {\tt toplabel} and {\tt bottomlabel} to specify
+%additional labels appearing near the top and bottom of the nodes,
+%respectively.
+
+Graphs and cluster subgraphs may also have labels. Graph labels
+appear, by default, centered below the graph. Setting {\tt labelloc=t}
+centers the label above the graph. Cluster labels appear within the
+enclosing rectangle, in the upper left corner. The value {\tt labelloc=b}
+moves the label to the bottom of the rectangle. The setting
+{\tt labeljust=r} moves the label to the right.
+
+The default font is 14-point Times-Roman, in black.
+Other font families, sizes and colors may be selected using the
+attributes {\tt fontname}, {\tt fontsize} and {\tt fontcolor}.
+Font names should be compatible with the target interpreter.
+It is best to use only the standard font families
+Times, Helvetica, Courier or Symbol as these are guaranteed to work
+with any target graphics language.
+For example, \verb"Times-Italic", \verb"Times-Bold", and \verb"Courier"
+are portable; {\tt AvanteGarde\-DemiOblique} isn't.
+
+For bitmap output, such as GIF or JPG, \dot\ relies on having these
+fonts available during layout. Most precompiled installations of
+Graphviz use the fontconfig library for matching font names to
+available fontfiles. fontconfig comes with a set of utilities for
+showing matches and installing fonts. Please refer to the fontconfig
+documentation, or the external Graphviz FontFAQ or for further details.
+If Graphviz is built without fontconfig (which usually means you
+compiled it from source code on your own), the {\tt fontpath} attribute
+can specify a list of directories\footnote{For Unix-based systems, this is
+a concatenated list of pathnames, separated by colons. For Windows-based
+systems, the pathnames are separated by semi-colons.} which should be
+searched for the font files. If this is not set,
+\dot\ will use the DOTFONTPATH environment variable or, if this is not
+set, the GDFONTPATH environment variable. If none of these is set, \dot\
+uses a built-in list.
+
+Edge labels are positioned near the center of the edge. Usually, care
+is taken to prevent the edge label from overlapping edges and
+nodes. It can still be difficult, in a complex graph, to be certain
+which edge a label belongs to. If the {\tt decorate} attribute is set
+to true, a line is drawn connecting the label to its edge. Sometimes
+avoiding collisions among edge labels and edges forces the
+drawing to be bigger than desired. If {\tt labelfloat=true},
+\dot\ does not try to prevent such overlaps, allowing a more compact
+drawing.
+
+An edge can also specify additional labels, using {\tt headlabel} and
+{\tt taillabel}, which are be placed near the ends of the edge.
+The characteristics of these labels are specified using the attributes
+{\tt labelfontname}, {\tt labelfontsize} and {\tt labelfontcolor}.
+These labels are placed near the intersection of the edge and the node
+and, as such, may interfere with them. To tune a drawing, the user can
+set the {\tt labelangle} and {\tt labeldistance} attributes.
+The former sets the angle, in degrees, which the label is rotated from
+the angle the edge makes incident with the node.
+The latter sets a multiplicative scaling factor to adjust the distance
+that the label is from the node.
+
+\begin{table}[p]
+\begin{tabular}[t]{|l|l|p{3.0in}|} \hline
+Name & Default & Values \\ \hline
+%{\tt bottomlabel} & & auxiliary label for nodes of {\tt shape} M* \\
+{\tt color} & {\tt black} & node shape color \\
+{\tt colorscheme} & X11 & scheme for interpreting color names \\
+{\tt comment} & & any string (format-dependent) \\
+{\tt distortion} & {\tt 0.0} & node distortion for {\tt shape=polygon} \\
+{\tt fillcolor} & {\tt lightgrey/black} & node fill color \\
+{\tt fixedsize} & false & label text has no affect on node size \\
+{\tt fontcolor} & {\tt black} & type face color \\
+{\tt fontname} & {\tt Times-Roman} & font family \\
+{\tt fontsize} & {\tt 14} & point size of label \\
+{\tt group} & & name of node's horizontal alignment group \\
+{\tt height} & {\tt .5} & height in inches \\
+{\tt id} & & any string (user-defined output object tags) \\
+{\tt image} & & image file name \\
+{\tt imagescale} & false & true, width, height, both \\
+{\tt label} & node name & any string \\
+{\tt labelloc} & c & node label vertical alignment \\
+{\tt layer} & overlay range & {\tt all}, {\it id} or {\it id:id} \\
+{\tt margin} & 0.11,0.55 & space around label \\
+{\tt nojustify} & false & if true, justify to label, not node \\
+{\tt orientation} & {\tt 0.0} & node rotation angle \\
+{\tt penwidth} & 1.0 & width of pen for drawing boundaries, in points \\
+{\tt peripheries} & {\tt shape-dependent} & number of node boundaries \\
+{\tt pos} & & input coordinate \\
+{\tt regular} & false & force polygon to be regular \\
+{\tt root} & false & set center node in circo and twopi \\
+{\tt samplepoints} & 8 or 20 & number vertices to convert circle or ellipse \\
+{\tt shape} & {\tt ellipse} & node shape; see Section~\ref{sect:shape} and
+Appendix~\ref{app:shapes}\\
+% {\tt shapefile} & & (deprecated, shape file)\\
+{\tt sides} & {\tt 4} & number of sides for {\tt shape=polygon} \\
+{\tt skew} & {\tt 0.0} & skewing of node for {\tt shape=polygon} \\
+{\tt sortv} & & sort key to control array packing order \\
+{\tt style} & & graphics options, e.g. {\tt bold, dotted, filled};
+cf. Section~\ref{sect:style} \\
+{\tt target} & & if URL is set, determines browser window for URL \\
+{\tt tooltip} & label & tooltip annotation \\
+%{\tt toplabel} & & auxiliary label for nodes of {\tt shape} M* \\
+{\tt URL} & & URL associated with node (format-dependent) \\
+{\tt width} & {\tt .75} & width in inches \\
+{\tt z} & {\tt 0.0} & z coordinate (deprecated, use {\tt pos}, {\tt dim}) \\
+\hline
+\end{tabular}
+\caption{Node attributes}
+\label{tab:nattr}
+\end{table}
+
+\begin{table}[p]
+\begin{tabular}[t]{|l|l|p{3.5in}|} \hline
+Name & Default & Values \\ \hline
+{\tt arrowhead} & normal & style of arrowhead at head end \\
+{\tt arrowsize} & {\tt 1.0} & scaling factor for arrowheads \\
+{\tt arrowtail} & normal & style of arrowhead at tail end \\
+{\tt color} & {\tt black} & edge stroke color \\
+{\tt colorscheme} & X11 & scheme for interpreting color names \\
+{\tt comment} & & any string (format-dependent) \\
+{\tt constraint} & true & use edge to affect node ranking \\
+{\tt decorate} & & if set, draws a line connecting labels with their edges \\
+{\tt dir} & {\tt forward} & {\tt forward}, {\tt back}, {\tt both}, or {\tt none} \\
+{\tt edgeURL} & & URL attached to non-label part of edge \\
+{\tt edgehref} & & synonym for edgeURL \\
+{\tt edgetarget} & & if URL is set, determines browser window for URL \\
+{\tt edgetooltip} & label & tooltip annotation for non-label part of edge \\
+{\tt fontcolor} & {\tt black} & type face color \\
+{\tt fontname} & {\tt Times-Roman} & font family \\
+{\tt fontsize} & {\tt 14} & point size of label \\
+{\tt headclip} & true & if false, edge is not clipped to head node boundary \\
+{\tt headhref} & & synonym for headURL \\
+{\tt headlabel} & & label placed near head of edge \\
+{\tt headport} & & {\tt n,ne,e,se,s,sw,w,nw}\\
+{\tt headtarget} & & if headURL is set, determines browser window for URL \\
+{\tt headtooltip} & label & tooltip annotation near head of edge \\
+{\tt headURL} & & URL attached to head label if output format is {\tt ismap} \\
+{\tt href} & & alias for URL \\
+{\tt id} & & any string (user-defined output object tags) \\
+{\tt label} & & edge label \\
+{\tt labelangle} & {\tt -25.0} & angle in degrees which head or tail label
+is rotated off edge \\
+{\tt labeldistance} & {\tt 1.0} & scaling factor for distance of head or tail label from node \\
+{\tt labelfloat} & false & lessen constraints on edge label placement \\
+{\tt labelfontcolor} & {\tt black} & type face color for head and tail labels\\
+{\tt labelfontname} & {\tt Times-Roman} & font family for head and tail labels\\
+{\tt labelfontsize} & {\tt 14} & point size for head and tail labels \\
+{\tt labelhref} & & synonym for labelURL \\
+{\tt labelURL} & & URL for label, overrides edge URL \\
+{\tt labeltarget} & & if URL or labelURL is set, determines browser window for URL \\
+{\tt labeltooltip} & label & tooltip annotation near label \\
+{\tt layer} & overlay range & {\tt all}, {\it id} or {\it id:id} \\
+{\tt len} & 1.0 & preferred edge length in neato \\
+{\tt lhead} & & name of cluster to use as head of edge \\
+{\tt ltail} & & name of cluster to use as tail of edge \\
+{\tt minlen} & {\tt 1} & minimum rank distance between head and tail \\
+{\tt penwidth} & 1.0 & width of pen for drawing edge stroke, in points \\
+{\tt samehead} & & tag for head node; edge heads with the same tag are merged onto
+the same port \\
+{\tt sametail} & & tag for tail node; edge tails with the same tag are merged onto
+the same port \\
+{\tt style} & & graphics options, e.g. {\tt bold, dotted, filled}; cf.
+Section~\ref{sect:style} \\
+{\tt tailclip} & true & if false, edge is not clipped to tail node boundary \\
+{\tt tailhref} & & synonym for tailURL \\
+{\tt taillabel} & & label placed near tail of edge \\
+{\tt tailport} & & {\tt n,ne,e,se,s,sw,w,nw}\\
+{\tt tailtarget} & & if tailURL is set, determines browser window for URL \\
+{\tt tailtooltip} & label & tooltip annotation near tail of edge \\
+{\tt tailURL} & & URL attached to tail label if output format is {\tt ismap} \\
+{\tt target} & & if URL is set, determines browser window for URL \\
+{\tt tooltip} & label & tooltip annotation \\
+{\tt weight} & {\tt 1} & integer cost of stretching an edge \\
+\hline
+\end{tabular}
+\caption{Edge attributes}
+\label{tab:eattr}
+\end{table}
+
+\begin{table}[p]\footnotesize
+\begin{tabular}[t]{|l|l|p{3.5in}|} \hline
+Name & Default & Values \\ \hline
+{\tt aspect} & & controls aspect ratio adjustment in dot \\
+{\tt bgcolor} & & background color for drawing, plus initial fill color \\
+{\tt center} & false & center drawing on {\tt page} \\
+{\tt clusterrank} & {\tt local} & may be {\tt global} or {\tt none} \\
+{\tt color} & {\tt black} & for clusters, outline color, and fill color
+if {\tt fillcolor} not defined \\
+{\tt colorscheme} & X11 & scheme for interpreting color names \\
+{\tt comment} & & any string (format-dependent) \\
+{\tt compound} & false & allow edges between clusters \\
+{\tt concentrate} & false & enables edge concentrators \\
+{\tt Damping} & 0.99 & solver parameter in neato \\
+{\tt defaultdist} & 1+(avg. len)*sqrt(|V|) & solver parameter in neato \\
+{\tt dim} & 2 & number of coordinate dimensions for layout \\
+{\tt dimen} & 2 & number of coordinate dimensions for rendering \\
+{\tt diredgeconstraints} & & if true, sets directed edges in neato ipsep \\
+{\tt dpi} & 96 & dots per inch for image output \\
+{\tt epsilon} & .0001 & neato terminating condition \\
+{\tt esep} & 3 & edge spline separation from nodes, in points \\
+{\tt fillcolor} & {\tt black} & cluster fill color \\
+{\tt fontcolor} & {\tt black} & type face color \\
+{\tt fontname} & {\tt Times-Roman} & font family \\
+{\tt fontnames} & & {\tt svg}, {\tt ps}, {\tt gd} (SVG only) \\
+{\tt fontpath} & & list of directories to search for fonts \\
+{\tt fontsize} & {\tt 14} & point size of label \\
+{\tt id} & & any string (user-defined output object tags) \\
+{\tt K} & 0.3 & solver parameter in fdp, sfdp \\
+{\tt label} & & any string \\
+{\tt labeljust} & centered & "l" and "r" for left- and right-justified
+cluster labels, respectively \\
+{\tt labelloc} & top & "t" and "b" for top- and bottom-justified cluster
+labels, respectively \\
+{\tt landscape} & & if true, means orientation=landscape \\
+{\tt layers} & & {\it id:id:id...} \\
+{\tt layersep} & : & specifies separator character to split {\tt layers} \\
+{\tt layout} & & layout module: {\tt dot}, {\tt neato}, etc. (try dot -K?) \\
+{\tt margin} & {\tt .5} & margin included in {\tt page}, inches \\
+{\tt maxiter} & & terminating condition for solver \\
+{\tt mclimit} & {\tt 1.0} & scale factor for mincross iterations \\
+{\tt mindist} & {\tt 1.0} & minimum separation between all nodes (not dot)\\
+{\tt mode} & major & neato solve: major, KK, hier ipsep \\
+{\tt model} & shortpath & network distance model (also circuit and subset)\\
+{\tt nodesep} & {\tt .25} & separation between nodes, in inches. \\
+{\tt nojustify} & false & if true, justify to label, not graph \\
+{\tt normalize} & & if {\tt true} then adjust coordinates so first node is at the origin and first edge is horizontal \\
+{\tt nslimit} & & if set to {\it f}, bounds network simplex iterations by {\it (f)(number of nodes)} when setting x-coordinates \\
+{\tt nslimit1} & & if set to {\it f}, bounds network simplex iterations by {\it (f)(number of nodes)} when ranking nodes \\
+{\tt ordering} & & if {\tt out} out edge order is preserved \\
+{\tt orientation} & {\tt portrait} & if {\tt rotate} is not used and the value
+is {\tt landscape}, use landscape orientation \\
+{\tt outputorder} & breadthfirst & or nodesfirst, edgesfirst \\
+{\tt pack} & & if true, apply packing algorithm to components \\
+{\tt packMode} & & node, clust, graph, or \verb"array[_flags][%d]" \\
+{\tt page} & & unit of pagination, {\it e.g.} {\tt "8.5,11"} \\
+{\tt pagedir} & {\tt BL} & traversal order of pages \\
+{\tt pencolor} & black & color for drawing cluster boundaries \\
+{\tt penwidth} & 1.0 & width of pen for drawing boundaries, in points \\
+{\tt peripheries} & 1 & number of cluster boundaries \\
+{\tt quadtree} & & quadtree scheme to use (0=false, 1=true, 2=fast)\\
+{\tt quantum} & & if {\tt quantum} > 0.0, node label dimensions will be
+rounded to integral multiples of {\tt quantum} \\
+{\tt rank} & & {\tt same}, {\tt min}, {\tt max}, {\tt source} or {\tt sink} \\
+{\tt rankdir} & {\tt TB} & {\tt LR} (left to right) or {\tt TB} (top to bottom) \\
+{\tt ranksep} & {\tt .75} & separation between ranks, in inches. \\
+{\tt ratio} & & approximate aspect ratio desired, {\tt fill} or {\tt auto} \\
+{\tt remincross} & & if true and there are multiple clusters, re-run crossing
+minimization \\
+{\tt repulsiveforce} & 1.0 & parameter for force model \\
+{\tt rotate} & & If 90, set orientation to landscape \\
+{\tt samplepoints} & {\tt 8} & number of points used to represent ellipses
+and circles on output (cf. Appendix~\ref{sect:output} \\
+{\tt searchsize} & {\tt 30} & maximum edges with negative cut values to
+check when looking for a minimum one during network simplex \\
+{\tt sep} & 1 & margin around nodes in node overlap removal \\
+{\tt size} & & maximum drawing size, in inches \\
+{\tt smoothing} & & method for smoothing node distribution after layout \\
+{\tt sortv} & & sort key to control array packing order \\
+{\tt splines} & & draw edges as splines, polylines \\
+{\tt start} & & initial placement: regular, self, random \\
+{\tt style} & & graphics options, e.g. {\tt filled} for clusters \\
+{\tt stylesheet} & & pathname or URL to XML style sheet for SVG \\
+{\tt target} & & if URL is set, determines browser window for URL \\
+{\tt tooltip} & label & tooltip annotation for cluster \\
+{\tt truecolor} & & if set, force 24 bit or indexed color in image output \\
+{\tt viewport} & & clipping window on output \\
+{\tt voro_margin} & & scale up factor in Voronoi overlap removal \\
+{\tt URL} & & URL associated with graph (format-dependent) \\
+\hline
+\end{tabular}
+\caption{Graph attributes}
+\label{tab:gattr}
+\end{table}
+
+\subsection{Graphics Styles}
+\label{sect:style}
+
+Nodes and edges can specify a {\tt color} attribute, with black
+the default. This is the color used to draw the node's shape
+or the edge. A {\tt color} value can be a hue-saturation-brightness triple
+(three floating point numbers between 0 and 1, separated by commas);
+one of the colors names listed in Appendix~\ref{app:colors}
+(borrowed from some version of the X window system); or
+a red-green-blue (RGB) triple\footnote{A fourth form, RGBA, is also supported,
+which has the same format as RGB with an additional fourth hexadecimal
+number specifying alpha channel or transparency information.}
+(three hexadecimal number between 00 and FF, preceded by the character '\#').
+Thus, the values {\tt "orchid"}, {\tt "0.8396,0.4862,0.8549"} and
+{\tt "\#DA70D6"} are three ways to specify the same color.
+The numerical forms are convenient for scripts or tools that
+automatically generate colors.
+Color name lookup is case-insensitive and ignores non-alphanumeric
+characters, so \verb'warmgrey' and \verb'Warm_Grey' are equivalent.
+
+We can offer a few hints regarding use of color in graph drawings.
+First, avoid using too many bright colors.
+A ``rainbow effect'' is confusing.
+It is better to choose a narrower range of colors, or
+to vary saturation along with hue.
+Second, when nodes are filled with dark or very saturated
+colors, labels seem to be more readable with \verb"fontcolor=white"
+and \verb"fontname=Helvetica". (We also have PostScript functions
+for \dot\ that create outline fonts from plain fonts.)
+Third, in certain output formats, you can define your own color space.
+For example, if using PostScript for output, you can redefine
+\verb"nodecolor", \verb"edgecolor", or \verb"graphcolor"
+in a library file. Thus, to use RGB colors, place
+the following line in a file \verb"lib.ps".
+\begin{verbatim}
+ /nodecolor {setrgbcolor} bind def
+\end{verbatim}
+Use the \verb"-l" command line option to load this file.
+\begin{verbatim}
+ dot -Tps -l lib.ps file.dot -o file.ps
+\end{verbatim}
+
+The {\tt style} attribute controls miscellaneous graphics features of
+nodes and edges.
+This attribute is a comma-separated list of primitives with
+optional argument lists.
+The predefined primitives include \verb"solid", \verb"dashed", \verb"dotted",
+\verb"bold" and \verb"invis".
+The first four control line drawing in node boundaries and edges and
+have the obvious meaning. The value {\tt invis} causes the node or edge
+to be left undrawn.
+The style for nodes can also include \verb"filled",
+\verb"diagonals" and \verb"rounded".
+\verb"filled" shades inside the node
+using the color {\tt fillcolor}. If this is not set, the value of
+{\tt color} is used. If this also is unset,
+light grey\footnote{The default is black if the output format is MIF,
+or if the shape is {\tt point}.} is used as the default.
+The \verb"diagonals" style causes short diagonal lines to be drawn
+between pairs of sides near a vertex. The \verb"rounded" style rounds
+polygonal corners.
+
+User-defined style primitives can be implemented as custom
+PostScript procedures. Such primitives are executed inside the
+\verb"gsave" context of a graph, node, or edge, before any of its
+marks are drawn. The argument lists are translated to PostScript notation.
+For example, a node with \verb'style="setlinewidth(8)"' is drawn with a
+thick outline. Here, \verb"setlinewidth" is a PostScript built-in, but
+user-defined PostScript procedures are called the same way. The
+definition of these procedures can be given in a library file loaded
+using \verb"-l" as shown above.
+
+Edges have a \verb"dir" attribute to set arrowheads.
+\verb"dir" may be \verb"forward" (the default), \verb"back", \verb"both",
+or \verb"none". This refers only to where arrowheads are drawn, and does
+not change the underlying graph. For example, setting \verb"dir=back"
+causes an arrowhead to be drawn at the tail and no arrowhead at the head,
+but it does not exchange the endpoints of the edge. The attributes
+{\tt arrowhead} and {\tt arrowtail} specify the style of arrowhead,
+if any, which is used at the head and tail ends of the edge.
+Allowed values are {\tt normal}, {\tt inv}, {\tt dot}, {\tt invdot},
+{\tt odot}, {\tt invodot} and {\tt none} (cf. Appendix~\ref{app:arrows}).
+The attribute {\tt arrowsize} specifies a multiplicative factor affecting
+the size of any arrowhead drawn on the edge.
+For example, {\tt arrowsize=2.0} makes the arrow twice as long and twice
+as wide.
+
+In terms of style and color, clusters act somewhat like large box-shaped
+nodes, in that the cluster boundary is drawn using the cluster's
+{\tt color} attribute and, in general, the appearance of the
+cluster is affected the {\tt style}, {\tt color} and {\tt fillcolor}
+attributes.
+
+If the root graph has a {\tt bgcolor} attribute specified, this color is used
+as the background for the entire drawing, and also serves as the default
+fill color.
+
+\subsection{Drawing Orientation, Size and Spacing}
+
+Two attributes that play an important role in determining the size of
+a \dot\ drawing are {\tt nodesep} and {\tt ranksep}.
+The first specifies the minimum distance, in inches, between two
+adjacent nodes on the same rank.
+The second deals with rank separation, which is the minimum vertical space
+between the bottoms of nodes in one rank and the tops of nodes in the next.
+The {\tt ranksep} attribute sets the rank separation, in inches.
+Alternatively, one can have {\tt ranksep=equally}. This guarantees
+that all of the ranks are equally spaced, as measured from the
+centers of nodes on adjacent ranks. In this case, the rank separation
+between two ranks is at least the default rank separation. As the
+two uses of {\tt ranksep} are independent, both can be set at the
+same time. For example, {\tt ranksep="1.0 equally"} causes ranks to
+be equally spaced, with a minimum rank separation of 1 inch.
+
+Often a drawing made with the default node sizes and separations
+is too big for the target printer or for the space allowed for
+a figure in a document. There are several ways to try to deal with
+this problem. First, we will review how \dot\ computes the
+final layout size.
+
+A layout is initially made internally at its ``natural'' size,
+using default settings (unless {\tt ratio=compress} was set,
+as described below). There is no
+bound on the size or aspect ratio of the drawing, so if the graph
+is large, the layout is also large. If you don't specify {\tt size}
+or {\tt ratio}, then the natural size layout is printed.
+
+The easiest way to control the output size of the drawing is to
+set {\tt size="$x$,$y$"} in the graph file (or on the command line
+using \verb"-G").
+This determines the size of the final layout.
+For example, \verb'size="7.5,10"' fits on an 8.5x11 page
+(assuming the default page orientation)
+no matter how big the initial layout.
+
+\verb"ratio" also affects layout size.
+There are a number of cases, depending on the settings of {\tt size}
+and {\tt ratio}.
+
+{\bf Case 1.} \verb"ratio" was not set.
+If the drawing already fits within the given \verb"size", then nothing happens.
+Otherwise, the drawing is reduced uniformly enough to make the critical
+dimension fit.
+
+If \verb"ratio" was set, there are four subcases.
+
+{\bf Case 2a.} If \verb"ratio="$x$ where $x$ is a floating point number,
+then the drawing is scaled up in one dimension to achieve the requested
+ratio expressed as drawing $height/width$.
+For example, \verb"ratio=2.0" makes the drawing twice as high
+as it is wide. Then the layout is scaled using \verb"size" as in Case 1.
+
+{\bf Case 2b.} If \verb"ratio=fill" and \verb"size="$x,y$ was set,
+then the drawing is scaled up in one dimension to achieve the ratio
+$y/x$.
+Then scaling is performed as in Case 1.
+The effect is that all of the bounding box given by \verb"size" is filled.
+
+{\bf Case 2c.} If \verb"ratio=compress"
+and \verb"size="$x,y$ was set, then the initial layout is compressed
+to attempt to fit it in the given bounding box. This trades off
+layout quality, balance and symmetry in order to pack the layout more tightly.
+Then scaling is performed as in Case 1.
+
+{\bf Case 2d.} If \verb"ratio=auto" and the {\tt page} attribute is
+set and the graph cannot be drawn on a single page,
+then \verb"size" is ignored and \dot\ computes an ``ideal'' size.
+In particular, the size in a given dimension will be the smallest integral
+multiple of the page size in that dimension which is at least half
+the current size.
+The two dimensions are then scaled independently to the new size.
+\if 0
+{\bf I don't think this code takes into account page margins or that
+the output might be rotated. Should it?}
+\fi
+
+If \verb"rotate=90" is set, or {\tt orientation=landscape},
+then the drawing is rotated $90^\circ$ into landscape mode.
+The $X$ axis of the layout would be along the $Y$ axis of each page.
+This does not affect \dot's interpretation of \verb"size",
+\verb"ratio" or \verb"page".
+
+At this point, if \verb"page" is not set, then the final layout is
+produced as one page.
+
+If \verb"page="$x,y$ is set, then the layout is printed as a sequence
+of pages which can be tiled or assembled into a mosaic. Common settings
+are \verb'page="8.5,11"' or \verb'page="11,17"'. These values
+refer to the full size of the physical device; the actual area used
+will be reduced by the margin settings.
+(For printer output, the default is 0.5 inches;
+for bitmap-output, the $X$ and $Y$
+margins are 10 and 2 points, respectively.)
+For tiled layouts, it may be helpful to set smaller margins.
+This can be done
+by using the {\tt margin} attribute. This can take a single number,
+used to set both margins, or two numbers separated by a comma to set the
+$x$ and $y$ margins separately. As usual, units are in inches. Although one can
+set \verb"margin=0", unfortunately, many bitmap printers have an
+internal hardware margin that cannot be overridden.
+
+The order in which pages are printed can be controlled by the
+{\tt pagedir} attribute. Output is always done using a row-based or
+column-based ordering,
+and {\tt pagedir} is set to a two-letter code specifying the major
+and minor directions. For example, the default is {\tt BL}, specifying
+a bottom-to-top ({\tt B}) major order and a left-to-right ({\tt L})
+minor order. Thus,
+the bottom row of pages is emitted first, from left to right, then the
+second row up, from left to right, and finishing with the top row,
+from left to right. The top-to-bottom order is represented by {\tt T}
+and the right-to-left order by {\tt R}.
+
+If {\tt center=true} and the graph can be output on one page, using the
+default page size of 8.5 by 11 inches if {\tt page} is not set, the
+graph is repositioned to be centered on that page.
+
+A common problem is that a large graph drawn at a small size
+yields unreadable node labels.
+To make larger labels, something has to give.
+There is a limit to the amount of readable text that can fit on one page.
+Often you can draw a smaller graph by extracting an interesting
+piece of the original graph before running \dot.
+We have some tools that help with this.
+\begin{description}
+\item [sccmap] decompose the graph into strongly connected components
+\item [tred] compute transitive reduction (remove edges implied by transitivity)
+\item [gvpr] graph processor to select nodes or edges, and contract
+or remove the rest of the graph
+\item [unflatten] improve aspect ratio of trees by staggering the lengths
+of leaf edges
+\end{description}
+
+With this in mind, here are some thing to try on a given graph:
+\begin{enumerate}
+\item Increase the node \verb"fontsize".
+\item Use smaller \verb"ranksep" and \verb"nodesep".
+\item Use \verb"ratio=auto".
+\item Use \verb"ratio=compress" and give a reasonable \verb"size".
+\item A sans serif font (such as Helvetica) may be more readable than Times
+when reduced.
+\end{enumerate}
+
+\subsection{Node and Edge Placement}
+
+Attributes in \dot\ provide many ways to adjust the large-scale
+layout of nodes and edges, as well as fine-tune the drawing to
+meet the user's needs and tastes. This section discusses these
+attributes\footnote{For completeness, we note that \dot\ also provides
+access to various parameters which play technical roles in the
+layout algorithms. These include {\tt mclimit},
+{\tt nslimit}, {\tt nslimit1}, {\tt remincross} and {\tt searchsize}.}.
+
+Sometimes it is natural to make edges point from left to right
+instead of from top to bottom.
+If \verb"rankdir=LR" in the top-level graph, the drawing is rotated
+in this way. \verb"TB" (top to bottom) is the default. The mode
+\verb"rankdir=BT" is useful for drawing upward-directed graphs.
+For completeness, one can also have \verb"rankdir=RL".
+
+In graphs with time-lines, or in drawings that emphasize source and sink nodes,
+you may need to constrain rank assignments.
+The \verb"rank" of a subgraph may be set to {\tt same}, {\tt min},
+{\tt source}, {\tt max} or {\tt sink}.
+A value {\tt same} causes all the nodes in the subgraph to occur
+on the same rank. If set to {\tt min}, all the nodes in the subgraph
+are guaranteed to be on a rank at least as small as any other node in the
+layout\footnote{Recall that the minimum rank occurs at the top of a drawing.}.
+This can be made strict by setting {\tt rank=source}, which
+forces the nodes in the subgraph to be on some rank strictly smaller
+than the rank of any other nodes (except those also specified by
+{\tt min} or {\tt source} subgraphs).
+The values {\tt max} or {\tt sink} play an analogous role for the
+maximum rank.
+Note that these constraints induce equivalence classes of nodes. If one
+subgraph forces nodes {\tt A} and {\tt B} to be on the same rank, and
+another subgraph forces nodes {\tt C} and {\tt B} to share a rank, then
+all nodes in both subgraphs must be drawn on the same rank.
+Figures~\ref{fig:asde91} and \ref{fig:asde91drawing}
+illustrate using subgraphs for controlling rank assignment.
+
+\begin{figure}[p]
+\scriptsize
+\begin{verbatim}
+digraph asde91 {
+ ranksep=.75; size = "7.5,7.5";
+
+ {
+ node [shape=plaintext, fontsize=16];
+ /* the time-line graph */
+ past -> 1978 -> 1980 -> 1982 -> 1983 -> 1985 -> 1986 ->
+ 1987 -> 1988 -> 1989 -> 1990 -> "future";
+ /* ancestor programs */
+ "Bourne sh"; "make"; "SCCS"; "yacc"; "cron"; "Reiser cpp";
+ "Cshell"; "emacs"; "build"; "vi"; "<curses>"; "RCS"; "C*";
+ }
+
+ { rank = same;
+ "Software IS"; "Configuration Mgt"; "Architecture & Libraries";
+ "Process";
+ };
+
+ node [shape=box];
+ { rank = same; "past"; "SCCS"; "make"; "Bourne sh"; "yacc"; "cron"; }
+ { rank = same; 1978; "Reiser cpp"; "Cshell"; }
+ { rank = same; 1980; "build"; "emacs"; "vi"; }
+ { rank = same; 1982; "RCS"; "<curses>"; "IMX"; "SYNED"; }
+ { rank = same; 1983; "ksh"; "IFS"; "TTU"; }
+ { rank = same; 1985; "nmake"; "Peggy"; }
+ { rank = same; 1986; "C*"; "ncpp"; "ksh-i"; "<curses-i>"; "PG2"; }
+ { rank = same; 1987; "Ansi cpp"; "nmake 2.0"; "3D File System"; "fdelta";
+ "DAG"; "CSAS";}
+ { rank = same; 1988; "CIA"; "SBCS"; "ksh-88"; "PEGASUS/PML"; "PAX";
+ "backtalk"; }
+ { rank = same; 1989; "CIA++"; "APP"; "SHIP"; "DataShare"; "ryacc";
+ "Mosaic"; }
+ { rank = same; 1990; "libft"; "CoShell"; "DIA"; "IFS-i"; "kyacc"; "sfio";
+ "yeast"; "ML-X"; "DOT"; }
+ { rank = same; "future"; "Adv. Software Technology"; }
+
+ "PEGASUS/PML" -> "ML-X";
+ "SCCS" -> "nmake";
+ "SCCS" -> "3D File System";
+ "SCCS" -> "RCS";
+ "make" -> "nmake";
+ "make" -> "build";
+ .
+ .
+ .
+}
+\end{verbatim}
+\caption{Graph with constrained ranks}
+\label{fig:asde91}
+\end{figure}
+
+\begin{figure}[p]
+ \centerline {
+ \includegraphics[width=6in]{asde91}
+ }
+ \caption{Drawing with constrained ranks}
+ \label{fig:asde91drawing}
+\end{figure}
+
+In some graphs, the left-to-right ordering of nodes is important.
+If a subgraph has \verb"ordering=out", then out-edges within the
+subgraph that have the same tail node wll fan-out from left to right
+in their order of creation. (Also note that flat edges involving the
+head nodes can potentially interfere with their ordering.)
+
+There are many ways to fine-tune the layout of nodes and edges. For
+example, if the nodes of an edge both have the same {\tt group}
+attribute, \dot\ tries to keep the edge straight and avoid
+having other edges cross it.
+The {\tt weight} of an edge provides another way to keep edges
+straight. An edge's {\tt weight} suggests some measure of an edge's importance;
+thus, the heavier the weight, the closer together its nodes should be.
+\dot\ causes edges with heavier weights to be drawn shorter and straighter.
+
+Edge weights also play a role when nodes are constrained to the same rank.
+Edges with non-zero weight between these nodes
+are aimed across the rank in the same direction
+(left-to-right, or top-to-bottom in a rotated drawing) as far as possible.
+This fact may be exploited to adjust node ordering by placing
+invisible edges (\verb'style="invis"') where needed.
+
+The end points of edges adjacent to the same node can be constrained
+using the {\tt samehead} and {\tt sametail} attributes. Specifically,
+all edges with the same head and the same value of {\tt samehead}
+are constrained to intersect the head node at the same point. The
+analogous property holds for tail nodes and {\tt sametail}.
+
+During rank assignment, the head node of an edge is constrained to be
+on a higher rank than the tail node. If the edge has {\tt constraint=false},
+however, this requirement is not enforced.
+
+In certain circumstances, the user may desire that the end points of
+an edge never get too close. This can be obtained by setting the
+edge's {\tt minlen} attribute. This defines the minimum difference
+between the ranks of the head and tail. For example, if {\tt minlen=2},
+there will always be at least one intervening rank between the head and tail.
+Note that this is not concerned with the geometric distance between the
+two nodes.
+
+Fine-tuning should be approached cautiously. \dot\ works
+best when it can makes a layout without much ``help'' or
+interference in its placement of individual nodes and edges.
+Layouts can be adjusted somewhat by increasing the \verb"weight" of
+certain edges, or by creating invisible edges or nodes using \verb"style=invis",
+and sometimes even by rearranging the order of nodes and edges in the file.
+But this can backfire because the layouts are
+not necessarily stable with respect to changes in the input graph.
+One last adjustment can invalidate all previous changes and make
+a very bad drawing. A future project we have in mind is to combine
+the mathematical layout techniques of \dot\ with an interactive
+front-end that allows user-defined hints and constraints.
+
+\section{Advanced Features}
+
+\subsection{Node Ports}
+\label{sect:ports}
+
+A node port is a point where edges can attach to a node.
+(When an edge is not attached to a port, it is aimed at the node's center
+and the edge is clipped at the node's boundary.)
+
+Simple ports can be specified by using the {\tt headport}
+and {\tt tailport} attributes. These can be assigned one of the
+8 compass points {\tt "n"}, {\tt "ne"}, {\tt "e"}, {\tt "se"},
+{\tt "s"}, {\tt "sw"}, {\tt "w"} or {\tt "nw"}. The end of the
+node will then be aimed at that position on the node. Thus, if
+{\tt tailport=se}, the edge will connect to the tail node at
+its southeast ``corner''.
+
+Nodes with a {\tt record} shape use the record structure to define ports.
+As noted above,
+this shape represents a record as recursive lists of boxes. If
+a box defines a port name, by using the construct
+{\tt < {\it port\_name} > } in the box label,
+the center of the box can be used a port.
+(By default, the edge is clipped to the box's boundary.)
+This is done by modifying the node name with the
+port name, using the syntax {\tt {\it node\_name}:{\it port\_name}},
+as part of an edge declaration.
+Figure~\ref{fig:tree} illustrates the declaration and use of
+port names in record nodes, with the resulting drawing shown
+in Figure \ref{fig:treedrawing}.
+
+{\bf DISCLAIMER: At present, simple ports don't work as advertised, even when
+they should. There is also the case where we might not want them to work,
+e.g., when the tailport=n and the headport=s. Finally, in theory, dot
+should be able to allow both types of ports on an edge, since the notions
+are orthogonal. There is still the question as to whether the two syntaxes
+could be combined, i.e., treat the compass points as reserved port names,
+and allow nodename:portname:compassname.}
+
+\begin{figure}[p]\footnotesize
+\begin{verbatim}
+ 1: digraph g {
+ 2: node [shape = record,height=.1];
+ 3: node0[label = "<f0> |<f1> G|<f2> "];
+ 4: node1[label = "<f0> |<f1> E|<f2> "];
+ 5: node2[label = "<f0> |<f1> B|<f2> "];
+ 6: node3[label = "<f0> |<f1> F|<f2> "];
+ 7: node4[label = "<f0> |<f1> R|<f2> "];
+ 8: node5[label = "<f0> |<f1> H|<f2> "];
+ 9: node6[label = "<f0> |<f1> Y|<f2> "];
+ 10: node7[label = "<f0> |<f1> A|<f2> "];
+ 11: node8[label = "<f0> |<f1> C|<f2> "];
+ 12: "node0":f2 -> "node4":f1;
+ 13: "node0":f0 -> "node1":f1;
+ 14: "node1":f0 -> "node2":f1;
+ 15: "node1":f2 -> "node3":f1;
+ 16: "node2":f2 -> "node8":f1;
+ 17: "node2":f0 -> "node7":f1;
+ 18: "node4":f2 -> "node6":f1;
+ 19: "node4":f0 -> "node5":f1;
+ 20: }
+\end{verbatim}
+\caption{Binary search tree using records}
+\label{fig:tree}
+\end{figure}
+
+\begin{figure}[p]
+ \centerline {
+ \includegraphics[height=2.5in]{tree}
+ }
+ \caption{Drawing of binary search tree}
+ \label{fig:treedrawing}
+\end{figure}
+
+Figures~\ref{fig:structs} and \ref{fig:structdrawing}
+give another example of the use of record nodes and ports.
+This repeats the example of
+Figures~\ref{fig:record} and \ref{fig:recorddrawing}
+but now using ports as connectors for edges.
+Note that records sometimes look better if their input height is set
+to a small value, so the text labels dominate the actual size, as
+illustrated in Figure~\ref{fig:tree}. Otherwise the default node
+size ($.75$ by $.5$) is assumed, as in Figure~\ref{fig:structdrawing}.
+\begin{figure}[p]\footnotesize
+\begin{verbatim}
+1: digraph structs {
+2: node [shape=record];
+3: struct1 [shape=record,label="<f0> left|<f1> middle|<f2> right"];
+4: struct2 [shape=record,label="<f0> one|<f1> two"];
+5: struct3 [shape=record,label="hello\nworld |{ b |{c|<here> d|e}| f}| g | h"];
+6: struct1:f1 -> struct2:f0;
+7: struct1:f2 -> struct3:here;
+8: }
+\end{verbatim}
+\caption{Records with nested fields (revisited)}
+\label{fig:structs}
+\end{figure}
+\begin{figure}[p]
+ \centerline {
+ \includegraphics{structs}
+ }
+ \caption{Drawing of records (revisited)}
+ \label{fig:structdrawing}
+\end{figure}
+The example of Figures~\ref{fig:hashtable} and \ref{fig:hashtabledrawing}
+uses left-to-right drawing in a layout of a hash table.
+\begin{figure}[p]\footnotesize
+\begin{verbatim}
+ 1: digraph G {
+ 2: nodesep=.05;
+ 3: rankdir=LR;
+ 4: node [shape=record,width=.1,height=.1];
+ 5:
+ 6: node0 [label = "<f0> |<f1> |<f2> |<f3> |<f4> |<f5> |<f6> | ",height=2.5];
+ 7: node [width = 1.5];
+ 8: node1 [label = "{<n> n14 | 719 |<p> }"];
+ 9: node2 [label = "{<n> a1 | 805 |<p> }"];
+10: node3 [label = "{<n> i9 | 718 |<p> }"];
+11: node4 [label = "{<n> e5 | 989 |<p> }"];
+12: node5 [label = "{<n> t20 | 959 |<p> }"] ;
+13: node6 [label = "{<n> o15 | 794 |<p> }"] ;
+14: node7 [label = "{<n> s19 | 659 |<p> }"] ;
+15:
+16: node0:f0 -> node1:n;
+17: node0:f1 -> node2:n;
+18: node0:f2 -> node3:n;
+19: node0:f5 -> node4:n;
+20: node0:f6 -> node5:n;
+21: node2:p -> node6:n;
+22: node4:p -> node7:n;
+23: }
+\end{verbatim}\vspace*{-.25in}
+\caption{Hash table graph file}
+\label{fig:hashtable}
+\end{figure}
+
+\begin{figure}[p]
+ \centerline {
+ \includegraphics[height=2.5in]{hashtable}
+ }
+ \caption{Drawing of hash table}
+ \label{fig:hashtabledrawing}
+\end{figure}
+
+\subsection{Clusters}
+
+A cluster is a subgraph placed in its own distinct rectangle of the layout.
+A subgraph is recognized as a cluster when its name has the prefix
+\verb"cluster". (If the top-level graph has {\tt clusterrank=none},
+this special processing is turned off).
+Labels, font characteristics and the {\tt labelloc} attribute can
+be set as they would be for the top-level graph, though
+cluster labels appear above the graph by default.
+For clusters, the label is left-justified by default;
+if {\tt labeljust="r"}, the label is right-justified.
+The {\tt color} attribute specifies the color of the enclosing rectangle.
+In addition, clusters may have {\tt style="filled"}, in which case
+the rectangle is filled with the color specified by {\tt fillcolor}
+before the cluster is drawn. (If {\tt fillcolor} is not specified,
+the cluster's {\tt color} attribute is used.)
+
+Clusters are drawn by a recursive technique that computes a
+rank assignment and internal ordering of nodes within clusters.
+Figure~\ref{fig:clust1} through \ref{fig:callgraph} are cluster layouts
+and the corresponding graph files.
+
+\begin{figure}[p]
+\begin{minipage}[t]{2.5in}
+\footnotesize
+\begin{verbatim}
+digraph G {
+ subgraph cluster0 {
+ node [style=filled,color=white];
+ style=filled;
+ color=lightgrey;
+ a0 -> a1 -> a2 -> a3;
+ label = "process #1";
+ }
+
+ subgraph cluster1 {
+ node [style=filled];
+ b0 -> b1 -> b2 -> b3;
+ label = "process #2";
+ color=blue
+ }
+ start -> a0;
+ start -> b0;
+ a1 -> b3;
+ b2 -> a3;
+ a3 -> a0;
+ a3 -> end;
+ b3 -> end;
+
+ start [shape=Mdiamond];
+ end [shape=Msquare];
+}
+\end{verbatim}
+\end{minipage} \hspace{0.05in} \
+\parbox[t]{2.0in}{
+ \ \\
+ \centerline {
+ \includegraphics[width=1.9in]{clust1}
+ }
+}
+ \caption{Process diagram with clusters}
+ \label{fig:clust1}
+\end{figure}
+\clearpage
+
+\begin{figure}[p]
+\footnotesize
+\begin{verbatim}
+1:digraph G {
+2: size="8,6"; ratio=fill; node[fontsize=24];
+3:
+4: ciafan->computefan; fan->increment; computefan->fan; stringdup->fatal;
+5: main->exit; main->interp_err; main->ciafan; main->fatal; main->malloc;
+6: main->strcpy; main->getopt; main->init_index; main->strlen; fan->fatal;
+7: fan->ref; fan->interp_err; ciafan->def; fan->free; computefan->stdprintf;
+8: computefan->get_sym_fields; fan->exit; fan->malloc; increment->strcmp;
+9: computefan->malloc; fan->stdsprintf; fan->strlen; computefan->strcmp;
+10: computefan->realloc; computefan->strlen; debug->sfprintf; debug->strcat;
+11: stringdup->malloc; fatal->sfprintf; stringdup->strcpy; stringdup->strlen;
+12: fatal->exit;
+13:
+14: subgraph "cluster_error.h" { label="error.h"; interp_err; }
+15:
+16: subgraph "cluster_sfio.h" { label="sfio.h"; sfprintf; }
+17:
+18: subgraph "cluster_ciafan.c" { label="ciafan.c"; ciafan; computefan;
+19: increment; }
+20:
+21: subgraph "cluster_util.c" { label="util.c"; stringdup; fatal; debug; }
+22:
+23: subgraph "cluster_query.h" { label="query.h"; ref; def; }
+24:
+25: subgraph "cluster_field.h" { get_sym_fields; }
+26:
+27: subgraph "cluster_stdio.h" { label="stdio.h"; stdprintf; stdsprintf; }
+28:
+29: subgraph "cluster_<libc.a>" { getopt; }
+30:
+31: subgraph "cluster_stdlib.h" { label="stdlib.h"; exit; malloc; free; realloc; }
+32:
+33: subgraph "cluster_main.c" { main; }
+34:
+35: subgraph "cluster_index.h" { init_index; }
+36:
+37: subgraph "cluster_string.h" { label="string.h"; strcpy; strlen; strcmp; strcat; }
+38:}
+\end{verbatim}
+\caption{Call graph file}
+\label{fig:clust2}
+\end{figure}
+
+\begin{figure}[p]
+ \centerline {
+ \includegraphics[width=6.5in]{clust2}
+ }
+ \caption{Call graph with labeled clusters}
+ \label{fig:callgraph}
+\end{figure}
+
+If the top-level graph has the {\tt compound} attribute set to true,
+\dot\ will allow edges connecting nodes and clusters. This is accomplished
+by an edge defining an {\tt lhead} or {\tt ltail} attribute. The
+value of these attributes must be the name of a cluster containing the
+head or tail node, respectively. In this case, the edge is clipped at
+the cluster boundary. All other edge attributes, such as {\tt arrowhead}
+or {\tt dir}, are applied to the truncated edge. For example,
+Figure~\ref{fig:compound} shows a graph using the {\tt compound} attribute
+and the resulting diagram.
+
+\begin{figure}[p]
+\begin{minipage}[t]{2.25in}
+\begin{verbatim}
+digraph G {
+ compound=true;
+ subgraph cluster0 {
+ a -> b;
+ a -> c;
+ b -> d;
+ c -> d;
+ }
+ subgraph cluster1 {
+ e -> g;
+ e -> f;
+ }
+ b -> f [lhead=cluster1];
+ d -> e;
+ c -> g [ltail=cluster0,
+ lhead=cluster1];
+ c -> e [ltail=cluster0];
+ d -> h;
+}
+\end{verbatim}
+\end{minipage} \hspace{0.5in} \
+\parbox[t]{2.0in}{
+ \ \\
+ \centerline {
+ \includegraphics[width=2in]{compound}
+ }
+}
+ \caption{Graph with edges on clusters}
+ \label{fig:compound}
+\end{figure}
+
+\subsection{Concentrators}
+Setting \verb"concentrate=true" on the top-level graph enables
+an edge merging technique to reduce clutter in dense layouts.
+Edges are merged when they run parallel, have a common endpoint
+and have length greater than 1.
+A beneficial side-effect in fixed-sized layouts is that removal
+of these edges often permits larger, more readable labels.
+While concentrators in \dot\ look somewhat like Newbery's
+\cite{newbery:concentrators}, they are found by searching
+the edges in the layout, not by detecting complete bipartite graphs in
+the underlying graph. Thus the \dot\ approach runs much faster
+but doesn't collapse as many edges as Newbery's algorithm.
+
+\section{Command Line Options}
+
+By default, \dot\ operates in filter mode,
+reading a graph from {\tt stdin}, and
+writing the graph on {\tt stdout} in the \DOT\ format with
+layout attributes appended.
+\dot\ supports a variety of command-line options:
+
+{\tt-T{\it format}} sets the format of the output. Allowed values
+for {\it format} are:
+
+\begin{description}
+\item[{\tt canon}]
+Prettyprint input; no layout is done.
+\item[{\tt dot}]
+Attributed \DOT. Prints input with layout information attached as
+attributes, cf. Appendix~\ref{sect:output}.
+\item[{\tt fig}] FIG output.
+\item[{\tt gd}] GD format. This is the internal format used by the GD Graphics
+Library. An alternate format is {\tt gd2}.
+\item[{\tt gif}] GIF output.
+\item[{\tt hpgl}] HP-GL/2 vector graphic printer language for HP wide bed
+plotters.
+\item[{\tt imap}] Produces map files for server-side image
+maps. This can be combined with a graphical form of the output, e.g., using
+{\tt -Tgif} or {\tt -Tjpg}, in web pages to attach links to nodes and edges.
+The format {\tt ismap} is a predecessor of the {\tt imap} format.
+\item[{\tt cmap}] Produces HTML map files for client-side image maps.
+\item[{\tt mif}] FrameMaker MIF format. In this format, graphs can be
+loaded into FrameMaker and edited manually. MIF is limited to 8 basic colors.
+\item[{\tt mp}] MetaPost output.
+\item[{\tt pcl}] PCL-5 output for HP laser writers.
+\item[{\tt pdf}] Adobe PDF via the Cairo library. We have seen problems when embedding into other documents. Instead, use -Tps2 as described below.
+\item[{\tt pic}] PIC output.
+\item[{\tt plain}] Simple, line-based ASCII format. Appendix~\ref{app:plain}
+describes this output. An alternate format is {\tt plain-ext}, which
+provides port names on the head and tail nodes of edges.
+\item[{\tt png}] PNG (Portable Network Graphics) output.
+\item[{\tt ps}] PostScript (EPSF) output.
+\item[{\tt ps2}] PostScript (EPSF) output with PDF annotations. This output should be distilled into PDF, such as for pdflatex, before being included in
+a document. (Use ps2pdf; epstopdf doesn't handle \verb"%%BoundingBox: (atend)".)
+\item[{\tt svg}] SVG output. The alternate form {\tt svgz} produces
+compressed SVG.
+\item[{\tt vrml}] VRML output.
+\item[{\tt vtx}] VTX format for r Confluents's Visual Thought.
+\item[{\tt wbmp}] Wireless BitMap (WBMP) format.
+\end{description}
+
+{\tt-G{\it name}={\it value}} sets a graph attribute default value.
+Often it is convenient to set size, pagination, and related
+values on the command line rather than in the graph file.
+The analogous flags \verb"-N" or \verb"-E"
+set default node or edge attributes.
+Note that file contents override command line arguments.
+
+{\tt-l{\it libfile}} specifies a device-dependent graphics library
+file. Multiple libraries may be given. These names are passed to the code
+generator at the beginning of output.
+
+{\tt-o{\it outfile}} writes output into file {\it outfile}.
+
+\verb"-v" requests verbose output. In processing large layouts,
+the verbose messages may give some estimate of \dot's progress.
+
+\verb"-V" prints the version number and exits.
+
+\section{Miscellaneous}
+
+In the top-level graph heading, a graph may be declared a
+{\tt strict digraph}. This forbids the creation of self-arcs
+and multi-edges; they are ignored in the input file.
+
+Nodes, edges and graphs may have a {\tt URL} attribute. In certain
+output formats ({\tt ps2}, {\tt imap}, {\tt ismap}, {\tt cmap}, or {\tt svg}),
+this information is integrated in the output
+so that nodes, edges and clusters become active links
+when displayed with the appropriate tools. Typically, URLs attached to
+top-level graphs serve as base URLs, supporting relative URLs on
+components. When the output format is {\tt imap}, or {\tt cmap},
+a similar processing
+takes place with the {\tt headURL} and {\tt tailURL} attributes.
+
+For certain formats ({\tt ps}, {\tt fig}, {\tt mif}, {\tt mp},
+{\tt vtx} or {\tt svg}), {\tt comment} attributes can be used to
+embed human-readable notations in the output.
+
+\section{Conclusions}
+
+\dot\ produces pleasing hierarchical drawings and can be
+applied in many settings.
+
+Since the basic algorithms of \dot\ work well, we have a good basis for
+further research into problems such as methods for drawing large graphs
+and on-line (animated) graph drawing.
+
+\section{Acknowledgments}
+We thank Phong Vo for his advice
+about graph drawing algorithms and programming.
+The graph library uses Phong's splay tree dictionary library.
+Also, the users of \dag, the predecessor of \dot,
+gave us many good suggestions.
+Guy Jacobson and and Randy Hackbarth reviewed earlier
+drafts of this manual, and Emden contributed substantially to the
+current revision. John Ellson wrote the generalized polygon
+shape and spent considerable effort to make it robust and efficient.
+He also wrote the GIF and ISMAP generators and other tools
+to bring {\it graphviz} to the web.
+
+\clearpage
+\bibliography{graphdraw}
+
+\appendix
+\clearpage
+\section{Graph File Grammar}
+\label{grammar}
+
+\newcommand{\lopt}{[}
+\newcommand{\ropt}{]}
+\newcommand{\lgrp}{(}
+\newcommand{\rgrp}{)}
+\newcommand{\strict}{{\bf strict}}
+\newcommand{\graph}{{\bf graph}}
+\newcommand{\digraph}{{\bf digraph}}
+\newcommand{\node}{{\bf node}}
+\newcommand{\edge}{{\bf edge}}
+\newcommand{\subgraph}{{\bf subgraph}}
+
+The following is an abstract grammar for the \DOT\ language.
+Terminals are shown in bold font and nonterminals in italics.
+Literal characters are given in single quotes.
+Parentheses \lgrp\ and \rgrp\ indicate grouping when needed.
+Square brackets \lopt\ and \ropt\ enclose optional items.
+Vertical bars $|$ separate alternatives.
+
+\begin{tabular}{lll}
+
+{\it graph} & $\rightarrow$ & \lopt \strict \ropt\ \lgrp\digraph\ $|$ \graph\rgrp\ {\it id} '\{' {\it stmt-list} '\}' \\
+
+{\it stmt-list} & $\rightarrow$ & \lopt {\it stmt} \lopt';'\ropt\ \lopt {\it stmt-list}\ \ropt\ \ropt \\
+
+{\it stmt} & $\rightarrow$ & {\it attr-stmt} $|$ {\it node-stmt} $|$ {\it edge-stmt} $|$ {\it subgraph} $|$ {\it id} '=' {\it id} \\
+
+{\it attr-stmt} & $\rightarrow$ & \lgrp\graph\ $|$ \node\ $|$ \edge\rgrp\ {\it attr-list} \\
+
+{\it attr-list} & $\rightarrow$ & '[' \lopt {\it a-list} \ropt\ ']' \lopt {\it attr-list}\ropt \\
+
+{\it a-list} & $\rightarrow$ & {\it id} '=' {\it id} \lopt','\ropt\ \lopt {\it a-list}\ropt \\
+
+{\it node-stmt} & $\rightarrow$ & {\it node-id} \lopt{\it attr-list}\ropt \\
+
+{\it node-id} & $\rightarrow$ & {\it id} \lopt {\it port}\ropt \\
+{\it port} & $\rightarrow$ & {\it port-location} \lopt {\it port-angle}\ropt\
+ $|$ {\it port-angle} \lopt {\it port-location}\ropt \\
+
+{\it port-location} & $\rightarrow$ & ':' {\it id} $|$ ':' '(' {\it id} ',' {\it id} ')' \\
+{\it port-angle} & $\rightarrow$ & '@' {\it id} \\
+
+{\it edge-stmt} & $\rightarrow$ & \lgrp{\it node-id} $|$ {\it subgraph}\rgrp\ {\it edgeRHS} \lopt {\it attr-list}\ropt \\
+
+{\it edgeRHS} & $\rightarrow$ & {\it edgeop} \lgrp{\it node-id} $|$ {\it subgraph}\rgrp\ \lopt {\it edgeRHS}\ropt \\
+
+{\it subgraph} & $\rightarrow$ & \lopt \subgraph\ {\it id}\ropt\ '\{' {\it stmt-list} '\}' $|$ \subgraph\ {\it id} \\
+
+\end{tabular}
+
+An {\it id} is any alphanumeric string not beginning with a digit,
+but possibly including underscores; or a number; or any quoted
+string possibly containing escaped quotes.
+
+An {\it edgeop} is \verb"->" in directed graphs and \verb"--" in
+undirected graphs.
+
+The language supports C++-style comments: \verb"/* */" and \verb"//".
+
+Semicolons aid readability but are not required except in the rare case
+that a named subgraph with no body immediate precedes an anonymous
+subgraph, because under precedence rules this sequence is parsed as
+a subgraph with a heading and a body.
+
+Complex attribute values may contain characters, such as commas and
+white space, which are used in parsing the \DOT\ language. To avoid getting
+a parsing error, such values need to be enclosed in double quotes.
+
+\clearpage
+\section{Plain Output File Format ({\tt -Tplain})}
+\label{app:plain}
+{
+\parindent0pt
+
+The ``plain'' output format of \dot\ lists node and edge
+information in a simple, line-oriented style which is easy
+to parse by front-end components.
+All coordinates and lengths are unscaled and in inches.
+
+The first line is:
+
+\hspace{.5in}\verb"graph" {\it scalefactor width height}
+
+The {\it width} and {\it height} values give the width and the height
+of the drawing; the lower-left corner of the drawing is at the origin.
+The {\it scalefactor} indicates how much to scale all coordinates
+in the final drawing.
+
+The next group of lines lists the nodes in the format:
+
+\hspace{.5in}\verb"node" {\it name x y xsize ysize label style shape color fillcolor }
+
+The {\it name} is a unique identifier. If it contains whitespace or
+punctuation, it is quoted. The {\it x} and {\it y} values give the coordinates
+of the center of the node; the {\it width} and {\it height} give the
+width and the height. The remaining parameters provide the node's
+{\tt label}, {\tt style}, {\tt shape}, {\tt color} and {\tt fillcolor}
+attributes, respectively. If the node does not have a {\tt style} attribute,
+{\tt "solid"} is used.
+
+The next group of lines lists edges:
+
+\hspace{.5in}\verb"edge" {\it tail head $n$ $x_1$ $y_1$ $x_2$ $y_2$
+$\ldots$ $x_n$ $y_n$ {\rm [} label lx ly {\rm ]} style color }
+
+$n$ is the number of coordinate pairs that follow as B-spline
+control points. If the edge is labeled, then the label text and
+coordinates are listed next. The edge description is completed by
+the edge's {\tt style} and {\tt color}. As with nodes, if a {\tt style} is not
+defined, {\tt "solid"} is used.
+
+The last line is always:
+
+\hspace{.5in}\verb"stop"
+}
+
+\clearpage
+\section{Attributed \DOT\ Format ({\tt -Tdot})}
+\label{sect:output}
+
+This is the default output format. It reproduces the input,
+along with layout information for the graph. Coordinate values
+increase up and to the right. Positions are represented by two
+integers separated by a comma, representing the $X$ and $Y$ coordinates
+of the location specified in points (1/72 of an inch). A position
+refers to the center of its associated object.
+Lengths are given in inches.
+
+A {\tt bb} attribute is attached to the graph,
+specifying the bounding box of the drawing. If the graph has a label,
+its position is specified by the {\tt lp} attribute.
+
+Each node gets {\tt pos}, {\tt width} and {\tt height} attributes.
+If the node is a record, the record rectangles are given in the {\tt rects}
+attribute. If the node is polygonal and the {\tt vertices}
+attribute is defined in the input graph, this attribute contains the
+vertices of the node. The number of points produced for circles and ellipses
+is governed by the {\tt samplepoints} attribute.
+
+Every edge is assigned a {\tt pos} attribute, which consists of
+a list of $3n + 1$ locations. These are B-spline control points:
+points $p_0, p_1, p_2, p_3$ are the first Bezier spline,
+$p_3, p_4, p_5, p_6$ are the second, etc.
+Currently, edge points are listed top-to-bottom (or left-to-right)
+regardless of the orientation of the edge. This may change.
+
+In the {\tt pos} attribute, the list of control points might
+be preceded by a start point $p_s$ and/or an end point $p_e$. These have the
+usual position representation with a {\tt "s,"} or {\tt "e,"}
+prefix, respectively. A start point is present if there is an
+arrow at $p_0$.
+In this case, the arrow is from $p_0$ to $p_s$, where
+$p_s$ is actually on the node's boundary. The length and direction
+of the arrowhead
+is given by the vector $(p_s - p_0)$.
+If there is no arrow, $p_0$ is on the node's boundary.
+Similarly, the point $p_e$ designates an arrow at the other end of the
+edge, connecting to the last spline point.
+
+If the edge has a label, the label position is given in {\tt lp}.
+
+\clearpage
+\section{Layers}
+{\dot} has a feature for drawing parts of a single diagram on
+a sequence of overlapping ``layers.'' Typically the layers are
+overhead transparencies. To activate this feature, one must
+set the top-level graph's {\tt layers} attribute to a list of identifiers.
+A node or edge can then be assigned to a layer or range of layers
+using its {\tt layer} attribute..
+{\tt all} is a reserved name for all layers (and can be
+used at either end of a range, e.g {\tt design:all} or {\tt all:code}).
+For example:
+\begin{verbatim}
+ layers = "spec:design:code:debug:ship";
+ node90 [layer = "code"];
+ node91 [layer = "design:debug"];
+ node90 -> node91 [layer = "all"];
+ node92 [layer = "all:code"];
+\end{verbatim}
+In this graph, {\tt node91} is in layers {\tt design}, {\tt code}
+and {\tt debug}, while {\tt node92} is in layers {\tt spec},
+{\tt design} and {\tt code}.
+
+In a layered graph, if a node or edge has no layer assignment,
+but incident edges or nodes do, then its layer specification
+is inferred from these. To change the default so that nodes
+and edges with no layer appear on all layers, insert near
+the beginning of the graph file:
+
+\begin{verbatim}
+ node [layer=all];
+ edge [layer=all];
+\end{verbatim}
+
+There is currently no way to specify a set of layers that are
+not a continuous range.
+
+When PostScript output is selected, the color sequence for layers
+is set in the array {\tt layercolorseq}. This array is indexed
+starting from 1, and every element must be a 3-element array which can
+interpreted as a color coordinate. The adventurous may
+learn further from reading {\dot}'s PostScript output.
+
+% \clearpage % why does this create a blank page here?
+\section{Node Shapes}
+\label{app:shapes}
+\begin{center}
+\begin{tabular}{cccc}\footnotesize
+\includegraphics{box} & \includegraphics{polygon} & \includegraphics{ellipse} & \includegraphics{circle} \\
+box & polygon & ellipse & circle \\
+\includegraphics{point} & \includegraphics{egg} & \includegraphics{triangle} & \includegraphics{plaintext} \\
+point & egg & triangle & plaintext \\
+\includegraphics{diamond} & \includegraphics{trapezium} & \includegraphics{parallelogram} & \includegraphics{house} \\
+diamond & trapezium & parallelogram & house \\
+\includegraphics{hexagon} & \includegraphics{octagon} & \includegraphics{doublecircle} & \includegraphics{doubleoctagon} \\
+hexagon & octagon & doublecircle & doubleoctagon \\
+\includegraphics{tripleoctagon} & \includegraphics{invtriangle} & \includegraphics{invtrapezium} & \includegraphics{invhouse} \\
+tripleoctagon & invtriangle & invtrapezium & invhouse \\
+\includegraphics{Mdiamond} & \includegraphics{Msquare} & \includegraphics{Mcircle} & \\
+Mdiamond & Msquare & Mcircle & \\
+\includegraphics{record} & \includegraphics{Mrecord} & & \\
+record & Mrecord & & \\
+\end{tabular}
+\end{center}
+
+\clearpage
+\section{Arrowhead Types}
+\label{app:arrows}
+\begin{center}
+\begin{tabular}{ccc}
+\includegraphics{normal} & \includegraphics{dot} & \includegraphics{odot} \\
+normal & dot & odot \\
+\includegraphics{inv} & \includegraphics{invdot} & \includegraphics{invodot} \\
+inv & invdot & invodot \\
+\includegraphics{none} & & \\
+none & & \\
+\end{tabular}
+\end{center}
+
+\clearpage
+\section{Color Names}
+\label{app:colors}
+{\footnotesize
+\begin{tabular*}{\textwidth}{@{\extracolsep{\fill}}llll}
+{\bf Whites} & {\bf Reds} & {\bf Yellows} & turquoise[1-4] \cr
+antiquewhite[1-4] & coral[1-4] & darkgoldenrod[1-4] \cr
+azure[1-4] & crimson & gold[1-4] & {\bf Blues} \cr
+bisque[1-4] & darksalmon & goldenrod[1-4] & aliceblue \cr
+blanchedalmond & deeppink[1-4] & greenyellow & blue[1-4] \cr
+cornsilk[1-4] & firebrick[1-4] & lightgoldenrod[1-4] & blueviolet \cr
+floralwhite & hotpink[1-4] & lightgoldenrodyellow & cadetblue[1-4] \cr
+gainsboro & indianred[1-4] & lightyellow[1-4] & cornflowerblue \cr
+ghostwhite & lightpink[1-4] & palegoldenrod & darkslateblue \cr
+honeydew[1-4] & lightsalmon[1-4] & yellow[1-4] & deepskyblue[1-4] \cr
+ivory[1-4] & maroon[1-4] & yellowgreen & dodgerblue[1-4] \cr
+lavender & mediumvioletred & & indigo \cr
+lavenderblush[1-4] & orangered[1-4] & {\bf Greens} & lightblue[1-4] \cr
+lemonchiffon[1-4] & palevioletred[1-4] & chartreuse[1-4] & lightskyblue[1-4] \cr
+linen & pink[1-4] & darkgreen & lightslateblue[1-4] \cr
+mintcream & red[1-4] & darkolivegreen[1-4] & mediumblue \cr
+mistyrose[1-4] & salmon[1-4] & darkseagreen[1-4] & mediumslateblue \cr
+moccasin & tomato[1-4] & forestgreen & midnightblue \cr
+navajowhite[1-4] & violetred[1-4] & green[1-4] & navy \cr
+oldlace & & greenyellow & navyblue \cr
+papayawhip & {\bf Browns} & lawngreen & powderblue \cr
+peachpuff[1-4] & beige & lightseagreen & royalblue[1-4] \cr
+seashell[1-4] & brown[1-4] & limegreen & skyblue[1-4] \cr
+snow[1-4] & burlywood[1-4] & mediumseagreen & slateblue[1-4] \cr
+thistle[1-4] & chocolate[1-4] & mediumspringgreen & steelblue[1-4] \cr
+wheat[1-4] & darkkhaki & mintcream \cr
+white & khaki[1-4] & olivedrab[1-4] & {\bf Magentas} \cr
+whitesmoke & peru & palegreen[1-4] & blueviolet \cr
+ & rosybrown[1-4] & seagreen[1-4] & darkorchid[1-4] \cr
+{\bf Greys} & saddlebrown & springgreen[1-4] & darkviolet \cr
+darkslategray[1-4] & sandybrown & yellowgreen & magenta[1-4] \cr
+dimgray & sienna[1-4] & & mediumorchid[1-4] \cr
+gray & tan[1-4] & {\bf Cyans} & mediumpurple[1-4] \cr
+gray[0-100] & & aquamarine[1-4] & mediumvioletred \cr
+lightgray & {\bf Oranges} & cyan[1-4] & orchid[1-4] \cr
+lightslategray & darkorange[1-4] & darkturquoise & palevioletred[1-4] \cr
+slategray[1-4] & orange[1-4] & lightcyan[1-4] & plum[1-4] \cr
+ & orangered[1-4] & mediumaquamarine & purple[1-4] \cr
+{\bf Blacks} & & mediumturquoise & violet \cr
+black & & paleturquoise[1-4] & violetred[1-4] \cr
+\end{tabular*}
+}
+
+%\tableofcontents
+%\coversheet
+\end{document}
+%
+%END
projects / graphviz / commitdiff