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                   Quick Reference Guide for GraphViz
                           20 February 2002


Command-line Invocation

  ------------------------------------------------------------------------
All GraphViz programs have a similar invocation:
 cmd [ flags ] [ input files ]
If no input files are supplied, the program reads from stdin.

Flags

-Gname=value
     Set a graph attribute.
-Nname=value
     Set a default node attribute.
-Ename=value
     Set a default edge attribute.
-Tformat
     Set output language to one of the supported formats. By default,
     attributed dot is produced.
-V
     Emit version information and exit.
-llibfile
     User-supplied, device-dependent library files. Multiple libraries may
     be given. These names are passed to the code generator at the beginning
     of output.
-n[num]
     Sets no-op flag in neato. If set, neato assumes nodes have already been
     positioned and have a pos attribute giving this position. It then just
     computes the edge layouts and emits the graph in the appropriate
     format. If num is supplied and > 1, neato checks for previously
     positioned edges, with control points provided in the pos attribute. It
     uses these if given; otherwise, it computes the edge layout.
-ooutfile
     Write output to file outfile. By default, output goes to stdout.
-s[scale]
     Set input scale to scale. If this value is omitted, 72.0 is used. This
     number is used to convert the point coordinate units used in the pos
     attribute into inches. For example, dot -Tdot produces pos values in
     points, with 72 per inch. Thus, to use this output as input to neato
     -n, one needs -s (equivalently, -s72).
-v
     Verbose mode
-x
     In neato, on input, prune isolated nodes and peninsulas. This removes
     uninteresting graph structure and produces a less cluttered drawing.

Note that the file contents override the -G, -N and -E flags. In addition,
these flags cause the related attributes to be permanently attached to the
graph. Thus, if attributed dot is used for output, the graph will have these
attributes.

  ------------------------------------------------------------------------

The DOT Language

  ------------------------------------------------------------------------
digraph G {foo -> bar; ... }  or graph G { foo -- bar;  ...}

To connect all pairs:
    {foo bar}->{baz bart}

To make a chain of links:      
     foo->bar->baz

Commas inside [...] and semicolons inside {...} are optional.

Quotes are needed on attribute values to protect spaces, commas, periods, etc.

// C++ like comment: to end of line
/* C-like comment: between delimiters */

For a complete language description, see

  http://www.research.att.com/~erg/graphviz/info/lang.html

  ------------------------------------------------------------------------

Attributes

  ------------------------------------------------------------------------

       Name      Used By     Type         Default       Minimum    Notes
 Damping         G       double      0.99              0.0       neato only
 Epsilon         G       double      (.0001 * # nodes)           neato only
 URL             ENGC    string
 arrowhead       E       arrowType   normal
 arrowsize       E       double      1.0               0.0
 arrowtail       E       arrowType   normal
 bb              G       rect                                    write-only
 bgcolor         G       color
 bottomlabel     N       string      ""
 center          G       bool        false
 clusterrank     G       clusterMode local                       dot only
 color           ENC     color       black
 comment         ENG     string      ""
 compound        G       bool        false                       dot only
 concentrate     G       bool        false                       dot only
 constraint      E       bool        true                        dot only
 decorate        E       bool        false

 dir             E       dirType     forward(directed)
                                     none(undirected)
 distortion      N       double      0.0               -100.0

 fillcolor       NC      color       lightgrey(nodes)
                                     black(clusters)
 fixedsize       N       bool        false
 fontcolor       ENGC    color       black
 fontname        ENGC    string      "Times-Roman"
 fontpath        G       string      ""
 fontsize        ENGC    double      14.0              1.0
 group           N       string      ""                          dot only
 headURL         E       string      ""
 headlabel       E       string      ""
 headport        E       portPos     center
 height          N       double      0.5               0.02
 K               G       double      1.0               0.0       sfdp only

 label           ENGC    string      ""
                                     "\N" (nodes)
 labelangle      E       double      -25.0             -180.0
 labeldistance   E       double      1.0               0.0
 labelfloat      E       bool        false
 labelfontcolor  E       color       black
 labelfontname   E       string      "Times-Roman"
 labelfontsize   E       double      11.0              1.0
 labeljust       C       string      ""                          dot only

 labelloc        GC      string      "t"(clusters)               dot only
                                     "b"(root graphs)
 layer           EN      layerRange  ""
 layers          G       layerList   ""
 len             E       double      1.0                         neato only
 levels          G       int         MAXINT            0         sfdp only
 lhead           E       string      ""                          dot only
 lp              EGC     point                                   write-only
 ltail           E       string      ""                          dot only

 margin          G       double
                         pointf
 maxiter         G       int         MAXINT                      neato only
 mclimit         G       double      1.0                         dot only
 minlen          E       int         1                 0         dot only
 model           G       string      ""                          neato only
 nodesep         G       double      0.25              0.02      dot only
 normalize       G       bool        false                       neato only
 nslimit
 nslimit1        G       double                                  dot only
 ordering        G       string      ""                          dot only
 orientation     N       double      0.0               360.0
 orientation     G       string      ""

 overlap         G       string      ""                          neato/sfdp only
                         bool
 page            G       pointf
 pagedir         G       pagedir     BL
 peripheries     N       int                           0
 pin             N       bool                                    neato only

 pos             EN      point
                         splineType
 quadtree        G       string      ""                          sfdp only
 quantum         G       double      0.0               0.0
 rank            S       rankType                                dot only
 rankdir         G       rankdir     TB                          dot only
 ranksep         G       double      0.5               0.02
 ratio           G       double
 rects           N       rect                                    write-only
 regular         N       bool        false
 remincross      G       bool        false                       dot only
 repulsiveforce  G       double      1                 0.0       sfdp only
 rotate          G       int         0
 samehead        E       string      ""                          dot only
 sametail        E       string      ""                          dot only
 samplepoints    G       int         8
 searchsize      G       int         30                          dot only
 sep             G       double      0.01                        neato only
 shape           N       shape       ellipse
 shapefile       N       string      ""
 showboxes       ENG     int         0                 0         dot only
 sides           N       int         4                 0
 size            G       pointf
 skew            N       double      0.0               -100.0
 smoothing       G       string      ""                          sfdp only
 splines         G       bool        false                       neato only

 start           G       string      ""                          neato only
                         int
 style           ENC     style
 styleheet       G       style
 tailURL         E       string      ""
 taillabel       E       string      ""
 tailport        E       portPos     center
 toplabel        N       string      ""
 vertices        N       pointfList                              write-only
 voro_margin     G       double      0.05              0.0       neato only
 w               E       double      1.0                         neato only

 weight          E       double      1.0               0(dot)
                                                       1(neato)
 width           N       double      0.75              0.01

 z               N       double      0.0               -MAXFLOAT
                                                       -1000
           ------------------------------------------------------
For the bool type, TRUE values are represented by "true" (case-insensitive)
and any non-zero integer, and FALSE values by "false" (case-insensitive) and
zero.

In the Used By field, the characters E, N, G and C represent edges, nodes,
the root graph and cluster subgraphs, respectively. This field indicates
which graph component uses the attribute.
  ------------------------------------------------------------------------

Attribute Descriptions

Damping
     Factor damping force motions. On each iteration, a nodes movement is
     limited to this factor of its potential motion. By being less than 1.0,
     the system tends to ``cool'', thereby preventing cycling.
Epsilon
     Terminating condition. If the length squared of all energy gradients
     are < Epsilon, the algorithm stops.
URL
     Incorporated into device-dependent output. At present, used for ps2,
     i*map and svg. For ps2, URLs can be attached to nodes and the root
     graph. When distilled to PDF, such nodes are active links and the graph
     URL can be used as a base URL. For i*map, URLs can be attached to
     nodes, edges and the root graph. If the node or edge URL contains "\N",
     this is replaced by the object's name. For svg, URLs can be attached to
     nodes, edges and clusters, with "\N" replacement done for all three.
arrowhead
     Style of arrowhead on head of edge.
arrowsize
     Multiplicative scale factor for arrowheads.
arrowtail
     Style of arrowhead on tail of edge.
bb
     Bounding box of drawing in integer points.
bgcolor
     Color used as background for canvas, plus initial fill color.
bottomlabel
     Additional label near bottom of nodes of shape M*.
center
     If true, the drawing is centered in the output canvas.
clusterrank
     Mode used for handling clusters. If clusterrank is "local", a subgraph
     whose name begins with "cluster" is given special treatment. The
     subgraph is laid out separately, and then integrated as a unit into its
     parent graph, with a bounding rectangle drawn about it. If the cluster
     has a label parameter, this label is displayed within the rectangle.
     Note also that there can be clusters within clusters. At present, the
     modes "global" and "none" appear to be identical, both turning off the
     special cluster processing.
color
     Basic drawing color for graphics.
comment
     Comments are inserted into output. Device-dependent
compound
     If true, allow edges between clusters. (See lhead and ltail below.)
concentrate
     If true, use edge concentrators.
constraint
     If false, the edge is not used in ranking the nodes. For example, in
     the graph

       digraph G {
         a -> c;
         a -> b;
         b -> c [constraint=false];
       }


     the edge b -> c does not add a constraint during rank assignment, so
     the only constraints are that a be above b and c.
             
decorate
     If true, attach edge label to edge by a 2-segment polyline, underlining
     the label, then going to the closest point of spline.
dir
     Set edge type for drawing arrowheads.
distortion
     Distortion factor for shape=polygon. Positive values cause top part to
     be larger than bottom; negative values do the opposite.
fillcolor
     If fillcolor is not defined, color is used. If this is not defined, the
     default is used, except for shape=point or when the output format is
     MIF, which use black by default.
fixedsize
     If true, the node size is kept fixed and not expanded to contain the
     text label.
fontcolor
     Color used for text.
fontname
     Font used for text.
fontpath
     Directory list used by libgd to search for bitmap fonts. If fontpath is
     not set, the environment variable DOTFONTPATH is checked. If that is
     not set, GDFONTPATH is checked. If not set, libgd uses its compiled-in
     font path.
fontsize
     Font size, in points, used for text.
group
     If the end points of an edge belong to the same group, i.e., have the
     same group attribute, parameters are set to avoid crossings and keep
     the edges straight.
headURL
     For the output format imap, or cmap,  if headURL is defined, it is
     output as part of the head label of the edge. If headURL contains
     "\N", this will be replaced by the head label text.
headlabel
     Text label to be placed near head of edge.
headport
     Indicates where on the head node to attach the head of the edge. In the
     default case, the edge is aimed towards the center of the node, and
     then clipped at the node boundary.
height
     Height of node, in inches.
K    constant used in the Fruchterman-Reingold force directed model.
label
     Text label attached to objects. The escape sequences "\n", "\l" and
     "\r" divide the label into lines, centered, left-justified and
     right-justified, respectively. The escape sequence "\N" represents a
     node's name. If a node's shape is record, then the label can have a
     special format which describes the record layout.
labelangle
     Angle, in degrees, that the headlabel(taillabel) is rotated from the
     angle the edge makes incident with the head(tail) node, respectively.
labeldistance
     Multiplicative scaling factor adjusting the distance that the
     headlabel(taillabel) is the from head(tail) node.
labelfloat
     If true, allows edge labels to be less constrained in position. In
     particular, it may appear on top of other edges.
labelfontcolor
     Color used for headlabel and taillabel.
labelfontname
     Font used for headlabel and taillabel.
labelfontsize
     Font size, in points, used for headlabel and taillabel.
labeljust
     Justification for cluster labels. If "r", the label is right-justified
     within bounding rectangle; otherwise, left-justified.
labelloc
     Top/bottom placement of graph and cluster labels. If the attribute is
     "t", place label at the top; if the attribute is "b", place label at
     the bottom. By default, root graph labels go on the bottom and cluster
     labels go on the top.
layer
     Specifies layers in which the node or edge is present.
layers
     Specifies a linearly ordered list of layer names attached to the graph
     The graph is then output in separate layers. Only those components
     belonging to the current output layer appear. For more information, see
     the page How to use drawing layers (overlays).
len
     Preferred edge length, in inches.
levels
     Number of levels allowed in the multilevel scheme. Default is MAXINT.
lhead
     Logical head of an edge. When compound is true, if lhead is defined and
     is the name of a cluster containing the real head, the edge is clipped
     to the boundary of the cluster.
lp
     Label position, in points.
ltail
     Logical tail of an edge. When compound is true, if ltail is defined and
     is the name of a cluster containing the real tail, the edge is clipped
     to the boundary of the cluster.
margin
     Set x and y margins of canvas, in inches. In first case, both margins
     are set equal to the given value.
maxiter
     Sets the number of iterations used.
mclimit
     Multiplicative scale factor used to alter the MinQuit (default = 8) and
     MaxIter (default = 24) parameters used during crossing minimization.
     These correspond to the number of tries without improvement before
     quitting and the maximum number of iterations in each pass.
minlen
     Minimum edge length (rank difference between head and tail).
model
     If "circuit", use circuit resistance model to compute dissimilarity
     values; otherwise, use shortest path model.
nodesep
     Minimum space between two adjacent nodes in the same rank, in inches.
normalize
     If set, normalize coordinates of final layout so that the first point
     is at the origin, and then rotate the layout so that the first edge is
     horizontal.
nslimit ,
nslimit1
     Used to set number of iterations in network simplex applications.
     nslimit is used in computing node x coordinates, nslimit1 for ranking
     nodes. If defined, # iterations = nslimit(1) * # nodes; otherwise, #
     iterations = MAXINT.
ordering
     If "out" for a graph G, and n is a node in G, then edges n->* appear
     left-to-right in the same order in which they are defined.
orientation
     Angle, in degrees, used to rotate node shapes.
orientation
     If "[lL]*", set graph orientation to landscape Used only if rotate is
     not defined.
overlap
     If "scale", remove node overlaps by scaling; if converts to false,
     remove node overlaps by the Voronoi technique; otherwise, leave
     overlaps.
page
     Width and height of output pages, in inches. If this is set and is
     smaller than the size of the layout, a rectangular array of pages of
     the specified page size is overlaid on the layout, with origins aligned
     in the lower-left corner, thereby partitioning the layout into pages.
     The pages are then produced one at a time, in pagedir order.
pagedir
     If the page attribute is set and applicable, this attribute specifies
     the order in which the pages are emitted. This is limited to one of the
     8 row or column major orders.
peripheries
     Set number of peripheries used in polygonal shapes.
pin
     If true and the node has a pos attribute on input, neato prevents the
     node from moving from the input position. This property can also be
     specified in the pos attribute itself (cf. the point type).
pos
     Position of node, or spline control points, in points. In neato, pos
     can be used to set initial position of a node. Concerning this, see the
     -s command line flag.
quantum
     If quantum > 0.0, node label dimensions will be rounded to integral
     multiples of the quantum.
quadtree
     Quadtree scheme to use. Values are "normal" (default), "fast" or "none". 
     "fast" gives about 2-4 overall speedup compared with "normal", though 
     layout quality can suffer a little. 
rank
     Rank constraints on the nodes in a subgraph. If rank="same", all nodes
     are placed on the same rank. If rank="min", all nodes are placed on the
     minimum rank. If rank="source", all nodes are placed on the minimum
     rank, and the only nodes on the minimum rank belong to some subgraph
     whose rank attribute is "source" or "min". Analogous criteria hold for
     rank="max" and rank="sink". (Note: the minimum rank is topmost or
     leftmost, and the maximum rank is bottommost or rightmost.)
rankdir
     Sets direction of graph layout. If rankdir="LR", the graph is laid out
     from left to right, i.e., directed edges tend to go from left to right.
     By default, graphs are laid out from top to bottom.
ranksep
     In dot, this the gives desired rank separation, in inches. This is the
     minimum vertical distance between the bottom of the nodes in one rank
     and the tops of nodes in the next. If the value contains "equally", the
     centers of all ranks are spaced equally apart. Note that both settings
     are possible, e.g., ranksep = "1.2 equally". In twopi, specifies radial
     separation of ranks.
ratio
     Sets the aspect ratio (drawing height/drawing width) for the drawing.
     Note that this is adjusted before the size attribute constraints are
     enforced.

     If ratio is numeric, it is taken as the desired aspect ratio. Then, if
     the actual aspect ratio is less than the desired ratio, the drawing
     height is scaled up to achieve the desired ratio; if the actual ratio
     is greater than that desired ratio, the drawing width is scaled up.

     If ratio = "fill" and the size attribute is set, the drawing is scaled
     to achieve the aspect ratio implied by size. As size is set, when the
     drawing is later scaled to fit that rectangle, the resulting picture
     will fill the rectangle.

     If ratio = "compress" and the size attribute is set, dot attempts to
     compress the initial layout to fit in the given size. This achieves a
     tighter packing of nodes but reduces the balance and symmetry.

     If ratio = "auto", the page attribute is set and the graph cannot be
     drawn on a single page, then size is set to an ``ideal'' value. 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.
rects
     Rectangles for fields of records, in points.
regular
     If true, force polygon to be regular.
repulsiveforce
     The power of repulsive force used in an extended Fruchterman-Reingold 
     force directed model. Default is 1. Values larger than 1 tend to reduce 
     the warping effect at the expensive of less clustering.
remincross
     If true and there are multiple clusters, run cross minimization a
     second time.
rotate
     If 90, set drawing orientation to landscape.
samehead
     Edges with the same head and the same samehead value are aimed at the
     same point on the head.
sametail
     Edges with the same tail and the same sametail value are aimed at the
     same point on the tail.
samplepoints
     If the input graph defines the vertices attribute, and output is plain*
     or attributed dot, this give the number of points used to represent
     circles and ellipses. It plays the same role in neato, when adjusting
     the layout to avoid overlapping nodes.
searchsize
     During network simplex, maximum number of edges with negative cut
     values to search when looking for one with minimum cut value.
sep
     Fraction to increase polygons (multiply coordinates by 1 + sep) for
     purposes of determining overlap. Guarantees a minimal non-zero distance
     between nodes.
shape
     Set shape of node.
shapefile
     For output format is ps* or svg*, if non-empty, taken as a filename
     containing a device-dependent description of a node's shape.
showboxes
     Print guide boxes in PostScript at the beginning of routesplines if 1,
     or at the end if 2. (Debugging)
sides
     Number of sides if shape=polygon.
size
     Maximum width and height of drawing, inches. If defined and the drawing
     is too large, the drawing is uniformly scaled down so that it fits
     within the given size. Note that there is some interaction between the
     size and ratio attributes.
skew
     Skew factor for shape=polygon. Positive values skew top of polygon to
     right; negative to left.
smoothing
     A post processing step to smooth out uneven distribution of nodes. Possible
     values are "none" (default), "avg_dist", "graph_dist", "power_dist", "rng", 
     "spring" and "triangle".
splines
     If true, draw edges as splines. This requires non-overlapping nodes
     (cf. overlap).
start
     Parameter used to determine the initial layout of nodes. By default,
     nodes are randomly placed in a square whose sides have length (#
     nodes). The same seed is always used for the random number generator,
     so the initial placement is repeatable. If start converts to an
     integer, this is used as a seed value for the random number generator.
     If start is "regular", the nodes are placed regularly about a circle.
     Finally, if start is defined but is not one of the above cases, the
     current time is used to pick a seed.
style
     Set style for node or edge. For cluster subgraph, if "filled", the
     cluster box's background is filled.
stylesheet
     The URL of a CSS stylesheet to be referenced from the output file.
     Relevant only for SVG output.
tailURL
     When the output format is imap, or cmap, if tailURL is defined, it is
     output as part of the tail label of the edge. If tailURL
     contains "\N", this will be replaced by the tail label text.
taillabel
     Text label to be placed near tail of edge.
tailport
     Indicates where on the tail node to attach the tail of the edge.
toplabel
     Additional label near top of nodes of shape M*.
vertices
     If the input graph defines this attribute, the node is polynomial, and
     output is plain* or attributed dot, this attribute provides the
     coordinates of the vertices of the node's polynomial, in points. If the
     node is an ellipse or circle, the samplepoints attribute affects the
     output.
voro_margin
     Factor to scale up drawing to allow margin for expansion in Voronoi
     technique. dim' = (1+2*margin)*dim.
w
     Redundant definition of weight in neato, cf. bug 9.
weight
     Weight of edge. Usually, the heavier the weight, the shorter (and, in
     dot, straighter and more vertical) an edge is.
width
     Width of node, in inches.
z
     Provides z coordinate for the node when output format is VRML.

  ------------------------------------------------------------------------

Attribute Type Descriptions

arrowType
      "normal"         "inv"             

      "dot"            "invdot"          

      "odot"           "invodot"         

      "none"          
clusterMode
     "local","global","none"
color
      "#%2x%2x%2x"   RGB
      "#%2x%2x%2x%2x"RGBA
      "%lf,%lf,%lf"  HSV 0.0 <= values <= 1.0
      string         color name
dirType
     For an edge T -> H;

      "forward"         "back"         

      "both"            "none"         

     For undirected edges T -- H;, one of the nodes, usually the righthand
     one, is treated as the head for the purpose of interpreting "forward"
     and "back".
layerList
     list of strings separated by colons, tabs or spaces, defining layer
     names and implicitly numbered 1,2,...
layerRange
     layerId or layerId[:\t ]layerId,
     where layerId = "all", decimal integer or layer name. (An integer i
     corresponds to layer i.)
pagedir
     "BL", "BR", "TL", "TR", "RB", "RT", "LB", "LT". These specify the 8 row
     or column major orders for traversing a rectangular array, the first
     character corresponding to the major order and the second to the minor
     order. Thus, for "BL", the major order is from bottom to top, and the
     minor order is from left to right. This means the bottom row is
     traversed first, from left to right, then the next row up, from left to
     right, and so on, until the topmost row is traversed.
point
     "%d,%d"('!') representing the point (x,y). The optional '!' indicates
     the node position should not change (input-only).
pointf
     "%lf,%lf" representing the point (x,y).
pointfList
     list of pointf, separated by spaces.
portPos
     "n","ne","e","se","s","sw","w","nw" These correspond to the obvious
     compass points on the node.
rankType
     "same", "min", "source", "max", "sink"
rankdir
     "LR". Any other value corresponds to a top-down layout.
rect
     "%d,%d,%d,%d" The rect llx,lly,urx,ury gives the coordinates, in
     points, of the lower-left corner (llx,lly) and the upper-right corner
     (urx,ury).
shape
     A string specifying the shape of a node. There are three main types of
     shapes : polygon-based, record-based and PostScript-based.
splineType
     spline ( ';' spline )*
      where spline= (endp)? (startp)? point (triple)]*
       and triple = point point point
         and endp = "e,%d,%d"
       and startp = "s,%d,%d"
     If a spline has points p1 p2 p3 ... pn, (n = 1 (mod 3)), the points
     correspond to the control points of a B-spline from p1 to pn. If startp
     is given, it touches one node of the edge, and the arrowhead goes from
     p1 to startp. If startp is not given, p1 touches a node. Similarly for
     pn and endp.
style
     styleItem ( ',' styleItem )*
      where styleItem= name or name'('args')'
            and args = name ( ',' name )*
            and name = [^)(, ][^)(,]*
     At present, the recognized style names comprise "dashed", "dotted",
     "solid", "invis" and "bold" for nodes and edges, and "filled",
     "diagonals" and "rounded" for nodes only. Additional styles are
     available in device-dependent form. Style lists are passed to device
     drivers, which can use this to generate appropriate output.

     Note that, at present, "rounded" cancels "filled", except for circles
     and ellipses. This holds for the Mrecord shape, which is rounded by
     definition.

  ------------------------------------------------------------------------

Output Formats

  ------------------------------------------------------------------------
The output format is specified with the -Tlang flag on the command line,
                    where lang is one of the following:
                Command-line
                 parameter               Format
                   canon
                   cmap     Client-side imagemap
                    dot     DOT
                    fig     FIG
                    gd
                    gd2     GD/GD2 formats
                    gif     GIF
                   hpgl     HP-GL/2
                   imap     Server-side imagemap
                   ismap    Server-side imagemap (deprecated)
                    jpg
                   jpeg     JPEG
                    mif     FrameMaker MIF format
                    mp      MetaPost
                    pcl     PCL
                    pic     PIC
                   plain
                 plain-ext  Simple text format
                    png     Portable Network Graphics format
                    ps      PostScript
                    ps2     PostScript for PDF
                    svg
                   svgz     Scalable Vector Graphics
                   vrml     VRML
                    vtx     Visual Thought format
                   wbmp     Wireless BitMap format
  ------------------------------------------------------------------------

Format Descriptions

canon ,
dot
     These two formats produce output in variations of the dot language.
     Using canon produces a prettyprinted version of the input, with no
     layout performed.

     dot corresponds to attributed dot, and is the default output format. It
     reproduces the input, along with layout information for the graph. In
     particular, a 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 lp attribute.

     Each node gets pos, width and height attributes. If the node is a
     record, the record rectangles are given in the rects attribute. If the
     node is a polygon and the vertices attribute is defined, this attribute
     contains the vertices of the node.

     Every edge is assigned a pos attribute, and if the edge has a label,
     the label position is given in lp.
fig
     Outputs graphs in the FIG graphics language.
gd ,
gd2
     Output images in the GD and GD2 format. These are the internal formats
     used by the gd library. The latter is compressed.
gif
     Outputs GIF bitmap images.
hpgl
     Produces output in the HP-GL/2 vector graphic printer language.
imap
cmap
     Produces map files for server-side and client-side image maps,
     respectively. These can be used in a web page with a graphical
     form of the output, e.g. in JPEG or GIF format, to attach links
     to nodes and edges. For example, given the dot file

       /* x.dot */
       digraph G {
         URL="http://www.research.att.com/";
         command [URL="command.html"];
         command -> output [URL="colors.html"];
       }


     this can be processed twice:

       dot -Timap > x.map
       dot -Tgif > x.gif


     and then be referred to in a web page, such as

       <A HREF="x.map">
       <IMG SRC="x.gif" ISMAP>
       </A>


     URLs can be attached to the root graph, nodes and edges. If the URL of
     a node contains the escape sequence "\N", it will be replaced by the
     node's name. If an edge has a URL, various points along the edge (but
     not the head or tail) will link to it. In addition, if the edge has a
     label, that will link to the URL.

     As for the head of the edge, this is linked to the headURL, if set.
     Otherwise, it is linked to the edge's URL if that is defined. If the
     headURL contains the escape sequence "\N", it will be replaced by the
     headlabel, if defined. The analogous description holds for the tail,
     tailURL and taillabel.
ismap
     Produces HTML image map files. This is a predecessor (circa 1994) of
     the IMAP format. Most servers now user the latter. URLs can be attached
     to the root graph, nodes and edges. Since edge links are attached to
     edge labels, an edge must have a label for its URL to be used. For both
     nodes and edges, if the URL has the escape sequence "\N" embedded in
     its string, this will be replaced with the node or edge name.
jpg ,
jpeg
     Output JPEG compressed image files. This format relies on the
     installation having the JPEG library.
mif
     Generates Frame Maker MIF files.
mp
     Produces MetaPost output.
pcl
     Produces output in the PCL printer language. HP-GL is a subset of PCL,
     so that PCL output is the same as HP-GL, wrapped with some initial and
     final commands to set the printer to and from HP-GL mode.
pic
     Outputs in PIC, the picture description language in the troff-family
plain ,
plain-ext
     The plain and plain-ext formats produce output using a simple,
     line-based language. The latter format differs in that, on edges, it
     provides port names on head and tail nodes when applicable.

     There are four types of statements.

        graph scale width height
        node name x y width height label style shape color fillcolor
        edge tail head n x1 y1 .. xn yn [label xl yl] style color
        stop


     graph
          The width and height values give the width and height of the
          drawing. The lower left corner of the drawing is at the origin.
          The scale value indicates how the drawing should be scaled if a
          size attribute was given and the drawing needs to be scaled to
          conform to that size. If no scaling is necessary, it will be set
          to 1.0. Note that all graph, node and edge coordinates and lengths
          are given unscaled.
     node
          The name value is the name of the node, and x and y give the
          node's position. The width and height are the width and height of
          the node. The label, style, shape, color and fillcolor give the
          node's label, style, shape, color and fillcolor, respectively,
          using attribute default values where necessary. If the node does
          not have a style attribute, "solid" is used.
     edge
          The tail and head values give the names of the head and tail
          nodes. n is the number of control points defining the B-spline
          forming the edge. This is followed by 2*n numbers giving the x and
          y coordinates of the control points in order from tail to head. If
          the edge has a label, this comes next followed by the x and y
          coordinates of the label's position. The edge description is
          completed by the edge's style and color. As with nodes, if a style
          is not defined, "solid" is used.
     The output consists of one graph line, a sequence of node lines, one
     per node, a sequence of edge lines, one per edge, and a final stop
     line. All units are in inches, represented by a floating point number.
png
     Produces output in the PNG (Portable Network Graphics) format. PNG
     relies on having libz and the PNG library.
ps
     Produces PostScript output.
ps2
     Produces PostScript output with PDF notations. It is assumed the output
     will be directly converted into PDF format. The notations include PDF
     bounding box information, so that the resulting PDF file can be
     correctly used with pdf tools, such as pdflatex. In addition, if a node
     has a URL attribute, this gets translated into PDF code such that the
     node, when viewed in a PDF-viewer, e.g., acroread, is a link to the
     given URL. If a URL is attached to the graph, this serves as a base,
     such that relative URLs on nodes are derived from it.
svg ,
svgz
     Produce SVG output, the latter in compressed format. SVG relies on
     having libz.
vrml
     Outputs graphs in the VRML format. VRML relies on having the PNG
     library.
vtx
     Generates graph diagrams in the format for Confluents's Visual Thought.
wbmp
     Produces output in the Wireless BitMap (WBMP) format, optimized for
     mobile computing.

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