This module defines the overall types and methods that interact with them for the Graphviz library. The specifications are based loosely upon the information available at: http://graphviz.org/doc/info/lang.html

Printing of Dot code is done as strictly as possible, whilst parsing is as permissive as possible. For example, if the types allow it then "2" will be parsed as an Int value. Note that quoting and escaping of String values is done automagically.

A summary of known limitations/differences:

• When creating GraphID values for graphID and subGraphID, you should ensure that none of them have the same printed value as one of the nodeID values to avoid any possible problems.
• If you want any GlobalAttributes in a DotSubGraph and want them to only apply to that DotSubGraph, then you must ensure it does indeed have a valid GraphID.
• All DotSubGraphs with isCluster = True must have unique subGraphID values.
• If eventually outputting to a format such as SVG, then you should make sure that your DotGraph has a graphID, as that is used as the title of the resulting image.
• Whilst DotGraph, etc. are polymorphic in their node type, you should ensure that you use a relatively simple node type (that is, it only covers a single line, etc.).
• Also, whilst Graphviz allows you to mix the types used for nodes, this library requires/assumes that they are all the same type.
• DotEdge defines an edge (a, b) (with an edge going from a to b); in Dot parlance the edge has a head at a and a tail at b. Care must be taken when using the related Head* and Tail* Attributes. See the differences section in Data.GraphViz.Attributes for more information.
• It is common to see multiple edges defined on the one line in Dot (e.g. n1 -> n2 -> n3 means to create a directed edge from n1 to n2 and from n2 to n3). These types of edge definitions are parseable; however, they are converted to singleton edges.
• Cannot create edges with subgraphs/clusters as one of the end points.
• When either creating a DotGraph by hand or parsing one, it is possible to specify that directedGraph = d, but DotEdge values with directedEdge = not d.
• Nodes cannot have Port values.
• Cannot place items in an arbitrary order: in particular, this means that it is not possible to use the normal Graphviz hack of having graph attributes that do not apply to subgraphs/clusters by listing them after the subgraphs/clusters.
• The parser will strip out comments and convert multiline strings into a single line string. Pre-processor lines (i.e. those started by #) and string concatenation are not yet supported.

See Data.GraphViz.Attributes for more limitations.