Drawing graphs with dot
Contents
1. 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 gt ML X SCCS gt nmake SCCS 3D File System SCCS RCS make gt nmake make gt build Figure 9 Graph with constrained ranks past 1978 1980 1982 1983 1985 1986 1987 1988 1989 future dot User s Manual February 4 2002 19 SCCS make Bourne sh Reiser cpp Cshell build vi emacs RCS lt curses gt ld ksh IFS i d nmake Y C ncpp lt curses i gt ksh i Y Y DAG CSAS Ansi cpp fdelta f 3D File System nmake 2 0 Y CIA CIA APP 1 DOT DIA libft CoShell Software IS Architecture amp Libraries Adv Software Technology yacc cron SYNED IMX Y TTU Peggy 1 PG2 PEGASUS PML backtalk DataShare ryace Mosaic Y kyacc yeast Process Figure 10 Drawing with constrained ranks dot User s Manua2. a gt b a gt gt e Sard subgraph clusterl e gt Gi Gn mec b gt f lhead cluster1 d gt e e gt g ltail cluster0 Cry es lhead cluster1 ltail cluster0 Q V 0 Figure 20 Graph with edges on clusters dot User s Manual February 4 2002 31 to attach links to nodes and edges The format ismap is a predecessor of the imap format cmap Produces HTML map files for client side image maps jpg JPEG output jpeg is a synonym for jpg mif FrameMaker MIF format In this format graphs can be loaded into FrameMaker and edited manually MIF is limited to 8 basic colors mp MetaPost output pcl PCL 5 output for HP laser writers pic PIC output plain Simple line based ASCII format Appendix B describes this output An alternate formatis plain ext which provides port names on the head and tail nodes of edges png PNG Portable Network Graphics output ps PostScript EPSF output ps2 PostScript EPSF output with PDF annotations It is assumed that this output will be distilled into PDF svg SVG output The alternate form svgz produces compressed SVG vrml VRML output vtx VTX format for r Confluents s Visual Thought wbmp Wireless BitMap WBMP format Gname 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 N or E set defau
3. The attribute arrowsize specifies a multiplica tive factor affecting the size of any arrowhead drawn on the edge For example 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 color attribute and in general the appearance of the cluster is affected the style color and fillcolor attributes If the root graph has a bgcolor attribute specified this color is used as the background for the entire drawing and also serves as the default fill color 2 4 Drawing Orientation Size and Spacing Two attributes that play an important role in determining the size of a dot drawing are nodesep and ranksep The first specifies the minimum distance in inches between two adjacent nodes on the same rank The second deals with rank sepa ration which is the minimum vertical space between the bottoms of nodes in one rank and the tops of nodes in the next The ranksep attribute sets the rank separa tion in inches Alternatively one can have 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 The default is black if the output format is MIF or if the shape is point dot User s Manual February 4 2002 15 default rank separation As the two uses of ranksep
4. V subgraph id An id is any alphanumeric string not beginning with a digit but possibly in cluding underscores or a number or any quoted string possibly containing escaped quotes An edgeop is gt in directed graphs and in undirected graphs The language supports C style comments and Semicolons aid readability but are not required except in the rare case that a named subgraph with no body immediate precedes an anonymous subgraph be cause 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 dot User s Manual February 4 2002 35 B Plain Output File Format Tplain 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 graph scalefactor width height The width and height values give the width and the height of the drawing the lower left corner of the drawing is at the origin The scalefactor indicates how much to scale all coordinates in the final drawing The next group of lines lists the nodes in the format node name x y xsize ysize label style shape color fillcolor The name is a unique identifier
5. 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 minlen attribute This defines the minimum difference between the ranks of the head and tail For example if 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 be tween 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 weight of certain edges or by creating invisible edges or nodes using 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 mathemat ical layout techniques of dot with an interactive front end that allows user defined hints and constraints dot User s Manual February 4 2002 21 3 Advanced Features 3 1 Node 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 bo
6. node2 f0 gt node7 f1 18 node4 f2 gt node6 f1 19 node4 f0 gt node5 f1 20 Figure 11 Binary search tree using records Figure 12 Drawing of binary search tree dot User s Manual February 4 2002 23 OO 1 07 GI BR O NP digraph structs node shape structl struct2 struct3 structl structl record shape record label lt f0 gt left lt f1 gt middle f2 right shape record label lt f0 gt one fl two shape record label hello nworld b c lt here gt dle f g h fl Str uct2 t0 f2 gt struct3 here Figure 13 Records with nested fields revisited left middle right Figure 14 Drawing of records revisited dot User s Manual February 4 2002 NO NO PRO PDF WN Fr Oo AAA TFWNHrF QO i000 10 01 RUNE Ke digraph G nodesep 05 rankdir LR node node0 node nodel node2 node3 node4 node5 node6 node node0 nodeO0 nodeO0 nodeO0 nodeO0 node2 node4 shape record width 1 height 1 label width label label label label label label F0 fl gt 2 gt E5 F6 gt label x EO 1 5 nodel node2 node3 node4 noded p gt node6 n p gt node7 n lt n gt lt n gt lt n gt lt n gt lt n gt lt n gt lt n gt n n n n n SEIS n14 al 19 e5 t20 o15 s19 2
7. nodecolor setrgbcolor bind def Use the 1 command line option to load this file dot Tps 1l lib ps file dot o file ps The style attribute controls miscellaneous graphics features of nodes and edges This attribute is a comma separated list of primitives with optional argu ment lists The predefined primitives include solid dashed dotted bold and invis The first four control line drawing in node boundaries and edges and have the obvious meaning The value invis causes the node or edge to be left undrawn The style for nodes can also include illed diagonals and 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 dot User s Manual February 4 2002 11 Name Default Values bottomlabel auxiliary label for nodes of shape M color black node shape color comment any string format dependent distortion 0 0 node distortion for shape polygon fillcolor lightgrey black node fill color fixedsize false label text has no affect on node size fontcolor black type face color fontname Times Roman font family fontsize 14 point size of label group name of node s group height 25 height in inches label node name any string layer overlay range all id or id id orientation 0 0 node rotation angle peripheries shape dependent number of node boundaries regular false force po
8. ther research into problems such as methods for drawing large graphs and on line animated graph drawing 7 Acknowledgments We thank Emden Gansner and Phong Vo for their advice about graph drawing al gorithms 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 sug gestions Emden Gansner Guy Jacobson 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 graphviz to the web dot User s Manual February 4 2002 33 References Car80 GKN V93 New89 Nor92 STT81 War77 M Carpano Automatic display of hierarchized graphs for computer aided decision analysis IEEE Transactions on Software Engineering SE 12 4 538 546 April 1980 Emden R Gansner Eleftherios Koutsofios Stephen C North and Kiem Phong Vo A Technique for Drawing Directed Graphs IEEE Trans Sofware Eng 19 3 214 230 May 1993 Frances J Newbery Edge Concentration A Method for Clustering Directed Graphs In 2nd International Workshop on Software Con figuration Management pages 76 85 October 1989 Published as ACM SIGSOFT Software Engineering Notes vol 17 no 7 Novem ber 1989 Stephen C N
9. 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 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 1abelfloat true dot does not try to prevent such overlaps allowing a more compact drawing An edge can also specify additional labels using headlabel andtaillabel which are be placed near the ends of the edge The characteristics of these la bels are specified using the attributes labelfontname labelfontsize and 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 1abelangle and labeldistance attributes The former sets the angle in degrees which the label is rotated from the angle the edge makes incident with The escape sequence AN is an internal symbol for node names 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 dot User s Manual February 4 2002 10 the node The latter sets a multiplicative scaling factor to adjust the distance that the label is from the node 2 3 Graphics Styles Nodes and edges can specify a color attribut
10. the drawing is scaled up in one dimension to achieve the requested ratio expressed as drawing height width For example ratio 2 0 makes the drawing twice as high as it is wide Then the layout is scaled using size as in Case 1 Case 2b If ratio fill and size z y was set then the drawing is scaled up in one dimension to achieve the ratio y z Then scaling is performed as in Case 1 The effect is that all of the bounding box given by size is filled Case 2c If rat io compress and size z y was set then the initial layout is compressed to attempt to fit it in the given bounding box This trades off lay out quality balance and symmetry in order to pack the layout more tightly Then scaling is performed as in Case 1 Case 2d If rat io auto and the page attribute is set and the graph cannot be drawn on a single page then 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 rotate 90 is set or orientation landscape then the drawing is rotated 90 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 size ratio or dot User s Manual February 4 2002 16 page At this point if page is not set then the final layout is produced as one
11. 719 805 718 989 959 794 659 3 lt p gt lt p gt lt p gt lt p gt lt p gt lt p gt lt p gt y 24 4 lt f5 gt lt f6 gt height 2 5 Figure 15 Hash table graph file eo 959 al 805 ois 74 Figure 16 Drawing of hash table dot User s Manual February 4 2002 25 Labels font characteristics and the 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 label just r the label is right justified The color attribute specifies the color of the enclosing rectangle In addition clusters may have style filled in which case the rectangle is filled with the color specified by illcolor before the cluster is drawn If fillcolor is not specified the cluster s color attribute is used Clusters are drawn by a recursive technique that computes a rank assignment and internal ordering of nodes within clusters Figure 17 through 19 are cluster layouts and the corresponding graph files dot User s Manual February 4 2002 digraph G subgraph cluster0 node style filled color white style filled color lightgrey process 1 ag gt al gt a2 gt a3 label process 1 a0 subgraph cluster1 Y node style filled al b0 gt bl gt b2 gt b33 label process 2 CD
12. Command Line Options By default dot operates in filter mode reading a graph from st din and writing the graph on stdout in the DOT format with layout attributes appended dot supports a variety of command line options Tformat sets the format of the output Allowed values for format are canon Prettyprint input no layout is done dot Attributed DOT Prints input with layout information attached as attributes cf Appendix C fig FIG output gd GD format This is the internal format used by the GD Graphics Library An alternate format is gd2 gif GIF output hpgl HP GL 2 vector graphic printer language for HP wide bed plotters imap Produces map files for server side image maps This can be combined with a graphical form of the output e g using Tgif or T jpg in web pages dot User s Manual February 4 2002 28 digraph G size 8 6 ratio fill node fontsize 24 Ts 2 3 4 ciafan gt computefan fan increment computefan gt fan stringdup gt fatal 5 main exit main interp err main gt ciafan main gt fatal main gt malloc 6 7 8 9 main gt strcpy main getopt main init index main gt strlen fan gt fatal fan gt ref fan gt interp err ciafan gt def fan gt free computefan gt stdprintf computefan get sym fields fan gt exit fan gt malloc increment gt strcmp computefan malloc fan gt stdsprintf fan gt strlen computefan gt strcmp 10 comp
13. Drawing graphs with dot Emden Gansner and Eleftherios Koutsofios and Stephen North February 4 2002 Abstract dot draws directed graphs as hierarchies It runs as a command line pro gram 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 struc tures 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 98 seconds of user time on a 1 4 Ghz AMD Athlon dot User s Manual February 4 2002 2 1 Basic Graph Drawing 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 or PostScript which can be converted to PDF dot draws a graph in four main phases Knowing this helps you to understand what kind of layouts dot makes and how you can control them The layout proce dure 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 edg
14. If it contains whitespace or punctuation it is quoted The x and y values give the coordinates of the center of the node the width and height give the width and the height The remaining parameters provide the node s label style shape color and fillcolor attributes respectively If the node does not have a style attribute solid is used The next group of lines lists edges edge tail head n x1 Y T2 Y2 Ln Yn label Ix ly 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 de scription is completed by the edge s style and color As with nodes if a style is not defined solid is used The last line is always stop dot User s Manual February 4 2002 36 C Attributed DOT Format Tdot This is the default output format It reproduces the input along with layout infor mation 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 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 1p attribute Each node gets pos width and height attributes If the node is a record t
15. are independent both can be set at the same time For example 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 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 size or ratio then the natural size layout is printed The easiest way to control the output size of the drawing is to set size x y in the graph file or on the command line using G This determines the size of the final layout For example size 7 5 10 fits on an 8 5x11 page assuming the default page orientation no matter how big the initial layout ratio also affects layout size There are a number of cases depending on the settings of size and ratio Case 1 ratio was not set If the drawing already fits within the given size then nothing happens Otherwise the drawing is reduced uniformly enough to make the critical dimension fit If ratio was set there are four subcases Case 2a If ratio z where x is a floating point number then
16. butes dot User s Manual February 4 2002 14 rounded filled shades inside the node using the color fillcolor If this is not set the value of color is used If this also is unset light grey is used as the default The diagonals style causes short diagonal lines to be drawn between pairs of sides near a vertex The rounded style rounds polygonal corners User defined style primitives can be implemented as custom PostScript proce dures Such primitives are executed inside the 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 style setlinewidth 8 is drawn with a thick outline Here set1inewidth 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 1 as shown above Edges have a dir attribute to set arrowheads dir may be forward the default back both or none This refers only to where arrowheads are drawn and does not change the underlying graph For example setting di r 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 arrowhead and arrowtail specify the style of arrowhead if any which is used at the head and tail ends of the edge Allowed values are normal inv dot invdot odot invodot and none cf Appendix F
17. color blue Y UW start gt a0 start gt DU al gt b3 Y b2 gt a3 a3 a3 gt a0 a3 end p b3 d en 7 start shape Mdiamond KA end shape Msguare Figure 17 Process diagram with clusters 26 dot User s Manual February 4 2002 27 If the top level graph has the compound attribute set to true dot will allow edges connecting nodes and clusters This is accomplished by an edge defining an lhead or 1tail 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 arrowhead or dir are applied to the truncated edge For example Figure 20 shows a graph using the compound attribute and the resulting diagram 3 3 Concentrators Setting 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 New89 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 4
18. e with black the default This is the color used to draw the node s shape or the edge A color value can be a hue saturation brightness triple three floating point numbers between 0 and 1 sepa rated by commas one of the colors names listed in Appendix G borrowed from some version of the X window system or a red green blue RGB triple three hexadecimal number between 00 and FF preceded by the character Thus the values orchid 0 8396 0 4862 0 8549 and 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 warmgrey and Warm_Grey are equiv alent 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 Sec ond when nodes are filled with dark or very saturated colors labels seem to be more readable with fontcolor white and 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 exam ple if using PostScript for output you can redefine nodecolor edgecolor or graphcolor ina library file Thus to use RGB colors place the following line in a file 1ib ps
19. es The third step orders nodes within ranks to avoid crossings The fourth step sets X coordi nates 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 War77 Carpano Car80 and Sugiyama STT81 We refer the reader to GKNV93 for a thorough explanation of dot s algorithms dot accepts input in the DOT language cf Appendix A This language de scribes three kinds of objects graphs nodes and edges The main outermost graph can be directed digraph or undirected graph Because dot makes lay outs of directed graphs all the following examples use digraph A separate layout utility neato draws undirected graphs Nor92 Within a main graph a subgraph defines a subset of nodes and edges Figure 1 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 A node is created when its name first appears in the file An edge is created when nodes are joined by the edge operator In the example line 2 makes edges from main to parse and from parse to execute Running dot on this file call itgraph1 dot dot Tps graphl dot o graphl ps yields the drawing of Figure 2 The command line optio
20. for head and tail labels labelfontname Times Roman font family for head and tail labels labelfontsize 14 point size for head and tail labels layer overlay range all id or id id lhead name of cluster to use as head of edge ltail name of cluster to use as tail of edge minlen 1 minimum rank distance between head and tail samehead tag for head node edge heads with the same tag are merged onto the same port sametail tag for tail node edge tails with the same tag are merged onto the same port style graphics options e g bold dotted filled cf Section 2 3 taillabel label placed near tail of edge tailport n ne e se S Sw W nw tailURL URL attached to tail label if output format is ismap weight 1 integer cost of stretching an edge Table 2 Edge attributes dot User s Manual February 4 2002 13 Name Default Values bgcolor background color for drawing plus initial fill color center false center drawing on page clusterrank local may be global or none color black for clusters outline color and fill color if i11color not defined comment any string format dependent compound false allow edges between clusters concentrate false enables edge concentrators fillcolor black cluster fill color fontcolor black type face color fontname Times Roman font family fontpath list of directories to such for fonts fontsize 14 point size of label label any string labeljust left justified r for right
21. he record rectangles are given in the rect s attribute If the node is polygonal and the 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 samplepoints attribute Every edge is assigned a pos attribute which consists of a list of 3n 1 locations These are B spline control points points po p p2 p3 are the first Bezier spline p3 p4 ps pe 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 pos attribute the list of control points might be preceded by a start point ps and or an end point pe These have the usual position representation with a s or e prefix respectively A start point is present if there is an arrow at po In this case the arrow is from pg to ps where p is actually on the node s boundary The length and direction of the arrowhead is given by the vector ps po If there is no arrow po is on the node s boundary Similarly the point pe 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 1p dot User s Manual February 4 2002 37 D Layers dot has a feature for drawing parts of a single diagram on a sequence of overlapping Tayers Typically the layers are overhead transparencies To activa
22. ht ordering of nodes is important If a subgraph has ordering out then out edges within the subgraph that have the same tail For completeness we note that dot also provides access to various parameters which play techni cal roles in the layout algorithms These include mclimit nslimit nslimit1 remincross and searchsize TRecall that the minimum rank occurs at the top of a drawing dot User s Manual February 4 2002 18 digraph asde91 ranksep 75 size 7 5 7 5 node shape plaintext fontsize 16 the time line graph past gt 1978 1980 gt 1982 gt 1983 gt 1985 gt 1986 gt 1987 1988 gt 1989 1990 future ancestor programs Bourne sh make SCCS yacc cron Reiser cpp Oshell emacs build vi lt curses gt RCS gx rank same Software IS Configuration Mgt Architecture amp Libraries Process i 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 lt curses gt IMX SYNED rank same 1983 ksh IFS TTU rank same 1985 nmake Peggy rank same 1986 C ncpp ksh i lt curses i gt 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
23. hus skew can be used to turn a box into a parallelogram distortion shrinks the polygon from top to bottom with negative values causing the bottom to be larger than the top distortion turns a box into a trapezoid A variety of these polygonal attributes are illustrated in Figures 6 and 5 Record based nodes form the other class of node shapes These include the shapes record and 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 1abe1 which has the following schema rlabel field field field boxLabel rlabel boxLabel string string 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 boxLabel gives a name to the field and serves as a port name for the box cf Section 3 1 The second string is used as a label for the field it may contain the same escape sequences as multi line labels cf Section 2 2 The example of Figures 7 and 8 illustrates the use and some properties of records 22 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 label attribute as sh
24. justified cluster labels labelloc top r for right justified cluster labels layers id id id margin Fas margin included in page inches mclimit 1 0 scale factor for mincross iterations nodesep 25 separation between nodes in inches nslimit if set to f bounds network simplex iterations by f number of nodes when setting x coordinates nslimitl if set to f bounds network simplex iterations by f number of nodes when ranking nodes ordering if out out edge order is preserved orientation portrait if rotate is not used and the value is landscape use landscape orientation page unit of pagination e g 8 5 11 pagedir BL traversal order of pages quantum if quantum 0 0 node label dimensions will be rounded to integral multiples of quantum rank same min max source or sink rankdir TB LR left to right or TB top to bottom ranksep A separation between ranks in inches ratio approximate aspect ratio desired 111 or auto remincross if true and there are multiple clusters re run crossing minimization rotate If 90 set orientation to landscape samplepoints 8 number of points used to represent ellipses and circles on output cf Appendix C searchsize 30 maximum edges with negative cut values to check when looking for a minimum one during network simplex size maximum drawing size in inches style graphics options e g filled for clusters URL URL associated with graph format dependent Table 3 Graph attri
25. l February 4 2002 20 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 group attribute dot tries to keep the edge straight and avoid having other edges cross it The weight of an edge provides another way to keep edges straight An edge s 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 style invis where needed The end points of edges adjacent to the same node can be constrained using the samehead and sametail attributes Specifically all edges with the same head and the same value of samehead are constrained to intersect the head node at the same point The analogous property holds for tail nodes and 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 constraint false
26. l graph the drawing is rotated in this way TB top to bottom is the default BT seems potentially useful for drawing upward directed graphs but hasn t been implemented In some graphs you could achieve the same effect by reversing the endpoints of edges and setting their dir back We note that the setting of rankdir is complementary to how the final drawing may be rotated by orientation or rotate In graphs with time lines or in drawings that emphasize source and sink nodes you may need to constrain rank assignments The rank of a subgraph may be set to samerank minrank source maxrank or sink A value samerank causes all the nodes in the subgraph to occur on the same rank If set to minrank all the nodes in the subgraph are guaranteed to be on a rank at least as small as any other node in the layout This can be made strict by setting 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 minrank or source subgraphs The values maxrank or sink play an analogous role for the maxi mum rank Note that these constraints induce equivalence classes of nodes If one subgraph forces nodes A and B to be on the same rank and another subgraph forces nodes C and B to share a rank then all nodes in both subgraphs must be drawn on the same rank Figures 9 and 10 illustrate using subgraphs for controlling rank assignment In some graphs the left to rig
27. lt page size of 8 5 by 11 inches if 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 sccmap decompose the graph into strongly connected components tred compute transitive reduction remove edges implied by transitivity gpr graph processor to select nodes or edges and contract or remove the rest of the graph unflatten improve aspect ratio of trees by staggering the lengths of leaf edges With this in mind here are some thing to try on a given graph 1 Increase the node fontsize dot User s Manual February 4 2002 17 2 Use smaller ranksep and nodesep 3 Use ratio auto 4 Use ratio compress and give a reasonable size 5 Asans serif font such as Helvetica may be more readable than Times when reduced 2 5 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 Sometimes it is natural to make edges point from left to right instead of from top to bottom If rankdir LR in the top leve
28. lt node or edge attributes Note that file contents override command line arguments llibfile 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 ooutfile writes output into file outfile v requests verbose output In processing large layouts the verbose messages may give some estimate of dot s progress V prints the version number and exits dot User s Manual February 4 2002 32 5 Miscellaneous In the top level graph heading a graph may be declared a 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 URL attribute In certain output formats ps2 imap ismap cmap or svg this information is integrated in the out put 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 imap or cmap a similar processing takes place with the headURL and tailURL at tributes For certain formats ps fig mif mp vtx or svg comment attributes can be used to embed human readable notations in the output 6 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 fur
29. lygon to be regular shape ellipse node shape see Section 2 1 and Appendix E shapefile external EPSF or SVG custom shape file sides 4 number of sides for shape polygon skew 0 0 skewing of node for shape polygon style graphics options e g bold dotted filled cf Section 2 3 toplabel auxiliary label for nodes of shape M URL URL associated with node format dependent width 75 width in inches Zz 0 0 z coordinate for VRML output Table 1 Node attributes dot User s Manual February 4 2002 12 Name Default Values arrowhead normal style of arrowhead at head end arrowsize 1 0 scaling factor for arrowheads arrowtail normal style of arrowhead at tail end color black edge stroke color comment any string format dependent constraint true use edge to affect node ranking decorate if set draws a line connecting labels with their edges dir forward forward back both or none fontcolor black type face color fontname Times Roman font family fontsize 14 point size of label headlabel label placed near head of edge headport n ne e se S Sw W nw headURL URL attached to head label if output format is ismap label edge label labelangle 25 0 angle in degrees which head or tail label is rotated off edge labeldistance 1 0 scaling factor for distance of head or tail label from node labelfloat false lessen constraints on edge label placement labelfontcolor black type face color
30. multi line label Line 13 changes the default node to be a box filled with a shade of blue The node compare inherits these values 2 Drawing Attributes The complete list of attributes that affect graph drawing is summarized in Tables 1 2 and 3 2 1 Node Shapes Nodes are drawn by default with shape ellipse width 75 height 5 and labeled by the node name Other common shapes include box circle recordandplaintext A complete list of node shapes is given in Appendix E The node shape plaintext is of particularly interest in that it draws a node with out 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 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 ixedsize true in which case the width and height values are enforced Node shapes fall into two broad categories polygon based and record based All node shapes except record and 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 regular true the node is forced to be regular The parameter peripheries sets the number of boundary curves drawn For example a dou blecircle has peripherie
31. n Tps selects PostScript EPSF output 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 3 and 4 illustrate some layout attributes In the listing of Figure 3 line 2 sets the graph s dot User s Manual February 4 2002 1 digraph G 2 main gt Bx main 4 main gt 53 execute 6 execute Js init ON main gt 9s execute TOS 3 pars gt execute init cleanup make string printf make string printf compare Figure 1 Small graph Figure 2 Drawing of small graph dot User s Manual February 4 2002 4 size to 4 4 ininches 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 main is assigned shape box The edge in line 4 is straightened by increasing its weight the default is 1 The edge in line 6 is drawn as a dotted line Line 8 makes edges from execute to make string and print f In line 10 the default edge color is set to red This affects any edges created after this point in the file Line 11 makes a bold edge labeled 100 times Inline 12 node make_st ring is given a
32. orth Neato User s Guide Technical Report 59113 921014 14TM AT amp T Bell Laboratories Murray Hill NJ 1992 K Sugiyama S Tagawa and M Toda Methods for Visual Under standing of Hierarchical System Structures IEEE Transactions on Systems Man and Cybernetics SMC 11 2 109 125 February 1981 John Warfield Crossing Theory and Hierarchy Mapping IEEE Trans actions on Systems Man and Cybernetics SMC 7 7 505 523 July 1977 dot User s Manual February 4 2002 34 A Graph File Grammar 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 and indicate grouping when needed Square brackets and enclose optional items Vertical bars separate alternatives graph strict digraph graph id stmt list stmt list stmt 7 stmt list stmt attr stmt node stmt edge stmt subgraph id id attr stmt graph node edge attr list attr list T a list attr list a list id id attr list node stmt node id attr list node id id port port port location port angle port angle port location port location gt id z C id id y port angle Q id edge stmt node id subgraph edgeRHS attr list edgeRHS edgeop node id subgraph edgeRHS subgraph subgraph id stmt list
33. own in Figure 4 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 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 dot User s Manual February 4 2002 7 digraph G a gt D gt e gt das shape polygon sides 5 peripheries 3 color blue light style filled shape polygon sides 4 skew 4 label hello world shape invtriangle shape polygon sides 4 distortion 7 c 100 40 N HG anaw o Figure 5 Graph with polygonal shapes hello world Figure 6 Drawing of polygonal node shapes dot User s Manual February 4 2002 OO 1 07 GI BR O NP digraph structs shape record shape record label lt f0 gt left lt f1 gt mid dle f2 right shape record label lt f0 gt one lt f1 gt two node structl struct2 struct3 structl structl shape record label hello nworld gt struct2 gt structa Figure 7 Records with nested fields left middle right Figure 8 Drawing of records I b c here d e HI g hi dot User s Manual February 4 2002 9 Multi line labels can be created by using the escape sequences Xn X1 Nr to terminate lines that are centered or left o
34. page If page z y is set then the layout is printed as a seguence of pages which can be tiled or assembled into a mosaic Common settings are page 8 5 11 or 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 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 margin 0 un fortunately many bitmap printers have an internal hardware margin that cannot be overridden The order in which pages are printed can be controlled by the pagedir at tribute Output is always done using a row based or column based ordering and pagedir is set to a two letter code specifying the major and minor directions For example the default is BL specifying a bottom to top B major order and a left to right 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 T and the right to left order by R If center true and the graph can be output on one page using the defau
35. pezium parallelogram house hexagon octagon doublecircle doubleoctagon tripleoctagon invtriangle invtrapezium invhouse Mdiamond Msquare Mcircle record Mrecord dot User s Manual February 4 2002 39 m A w F Arrowhead Types normal dot odot inv invdot invodot none dot User s Manual February 4 2002 G Color Names Whites antiquewhite 1 4 azure 1 4 bisque 1 4 blanchedalmond cornsilk 1 4 floralwhite gainsboro ghostwhite honeydew 1 4 ivory 1 4 lavender lavenderblush 1 4 lemonchiffon 1 4 linen mintcream mistyrose 1 4 moccasin navajowhite 1 4 oldlace papayawhip peachpuff 1 4 seashell 1 4 snow 1 4 thistle 1 4 wheat 1 4 white whitesmoke Greys darkslategray 1 4 dimgray gray gray 0 100 lightgray lightslategray slategray 1 4 Blacks black Reds coral 1 4 crimson darksalmon deeppink 1 4 firebrick 1 4 hotpink 1 4 indianred 1 4 lightpink 1 4 lightsalmon 1 4 maroon 1 4 mediumvioletred orangered 1 4 palevioletred 1 4 pink 1 4 red 1 4 salmon 1 4 tomato 1 4 violetred 1 4 Browns beige brown 1 4 burlywood 1 4 chocolate 1 4 darkkhaki khaki 1 4 peru rosybrown 1 4 saddlebrown sandybrown sienna 1 4 tan 1 4 Oranges darkorange 1 4 orange 1 4 orangered 1 4 Yellows darkgoldenrod 1 4 gold 1 4 goldenrod 1 4 greenyellow lightgoldenrod 1 4 lightgoldenrodyellow lightyellow 1 4 palegoldenrod yellow 1 4 yellowgreen G
36. r right justified The node shape Mdiamond Msquare andMcircle usethe attributes toplabel and 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 labelloc t centers the label above the graph Cluster labels appear within the enclosing rectangle in the upper left corner The value 1abelloc b moves the label to the bottom of the rectangle The setting Label just 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 font name fontsize and 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 Times Italic Times Bold and Courier are portable Avant eGarde DemiOblique isn t For bitmap output such as GIF or JPG dot relies on having these fonts avail able during layout The fontpath attribute can specify a list of directories 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
37. rd nodes and ports This repeats the example of Figures 7 and 8 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 11 Otherwise the default node size 75 by 5 is assumed as in Figure 14 The example of Figures 15 and 16 uses left to right drawing in a layout of a hash table 3 2 Clusters A cluster is a subgraph placed in its own distinct rectangle of the layout A sub graph is recognized as a cluster when its name has the prefix cluster If the top level graph has clusterrank none this special processing is turned off dot User s Manual February 4 2002 1 digraph g 2 nod shape record height 1 3 nodeO label lt f0 gt fl G lt f2 gt 4 nodel label f0 lt f1 gt E f2 5 node2 label f0 lt f1 gt B lt f2 gt 6 node3 label f0 lt f1 gt F f2 J 7 node4 label f0 lt f1 gt R f2 J 8 node5 label f0 lt f1 gt H f2 J 9 node6 label f0 lt f1 gt Y f2 J 10 node7 label f0 fl A f2 11 node8 label f0 lt f1 gt C f2 J 12 node0 f2 gt node4 f1 13 node0 f0 gt node1 f1 14 nodel1 f0 gt node2 f1 15 nodel1 f2 gt node3 f1 16 node2 f2 gt node8 f1 17
38. reens chartreuse 1 4 darkgreen darkolivegreen 1 4 darkseagreen 1 4 forestgreen green 1 4 greenyellow lawngreen lightseagreen limegreen mediumseagreen mediumspringgreen mintcream olivedrab 1 4 palegreen 1 4 seagreen 1 4 springgreen 1 4 yellowgreen Cyans aquamarine 1 4 cyan 1 4 darkturquoise lightcyan 1 4 mediumaquamarine mediumturquoise paleturquoise 1 4 40 turquoise 1 4 Blues aliceblue blue 1 4 blueviolet cadetblue 1 4 cornflowerblue darkslateblue deepskyblue 1 4 dodgerblue 1 4 indigo lightblue 1 4 lightskyblue 1 4 lightslateblue 1 4 mediumblue mediumslateblue midnightblue navy navyblue powderblue royalblue 1 4 skyblue 1 4 slateblue 1 4 steelblue 1 4 Magentas blueviolet darkorchid 1 4 darkviolet magenta 1 4 mediumorchid 1 4 mediumpurple 1 4 mediumvioletred orchid 1 4 palevioletred 1 4 plum 1 4 purple 1 4 violet violetred 1 4
39. s 2 The orientation attribute specifies a clock wise rotation of the polygon measured in degrees There is a way to implement custom node shapes using shape epsf and the 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 dot User s Manual February 4 2002 5 1 digraph G 23 size 4 4 33 main shape box this is a comment 4 main parse weight 8 51 parse gt execute 6 main gt init style dotted as main cleanup 8 execute gt make string printf 9s init make string 10 edge color red so is this all les main gt printf style bold label 100 times 123 make_string label make a nstring 133 node shape box style filled color 7 3 1 0 14 execute gt compare 15 Jj Figure 3 Fancy graph Figure 4 Drawing of fancy graph dot User s Manual February 4 2002 6 The shape polygon exposes all the polygonal parameters and is useful for creating many shapes that are not predefined In addition to the parameters regular peripheries and orientation mentioned above polygons are parameter ized by number of sides sides skew and distortion 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 T
40. te this feature one must set the top level graph s layers attribute to a list of identifiers A node or edge can then be assigned to a layer or range of layers using its layer attribute all is areserved name for all layers and can be used at either end of a range e g design allorall code For example layers spec design code debug ship node90 layer code node91 layer design debug node90 node91 layer all node92 layer all code In this graph node91 is in layers design code and debug while node92 is in layers spec design and 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 node layer all edge layer all There is currently no way to specify a set of layers that are not a continuous range When PostScript output is selected the color seguence for layers is set in the array layercolorseq This array is indexed starting from 1 and every ele ment must be a 3 element array which can interpreted as a color coordinate The adventurous may learn further from reading dot s PostScript output dot User s Manual February 4 2002 38 E Node Shapes E OOO box polygon ellipse circle a plaintext e point triangle plaintext diamond tra
41. undary Simple ports can be specified by using the headport and tailport at tributes These can be assigned one of the 8 compass points n ne e se s sw w or nw The end of the node will then be aimed at that position on the node Thus if tailport se the edge will connect to the tail node at its southeast corner Nodes with a 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 lt port name gt in the box label the cen ter 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 node name port name as part of an edge declaration Figure 11 illustrates the declaration and use of port names in record nodes with the resulting drawing shown in Figure 12 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 Figures 13 and 14 give another example of the use of reco
42. utefan realloc computefan gt strlen debug gt sfprintf debug gt strcat 11 stringdup gt malloc fatal gt sfprintf stringdup gt strcpy stringdup gt strlen 12 fatal gt exit Tas 14 subgraph cluster error h label error h interp_err 15 16 subgraph cluster sfio h label sfio h sfprintf LT ia subgraph cluster_ciafan c label ciafan c ciafan computefan 194 increment 20 ZT subgraph cluster_util c label util c stringdup fatal debug 223 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 283 203 subgraph cluster lt libc a gt getopt 30 31 subgraph cluster stdlib h label stdlib h exit malloc free realloc 325 33 subgraph cluster main c main 34 35 subgraph cluster index h init index 36 d subgraph cluster string h label 2 string h strcpy strlen strcmp strcat 38 Figure 18 Call graph file dot User s Manual February 4 2002 29 main ciafan c getopt Cnerement gt error computefan 7 Figure 19 Call graph with labeled clusters dot User s Manual February 4 2002 30 digraph G compound true subgraph clusterO
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