Does the DOT language support variables / aliases?

Question

I'm trying to print out a directed graph, and I keep changing various node attributes such as color and shape. Is there some way to use a variable which is defined once and used for multiple nodes? Ideally I'd like something like this:

digraph g { 

building_color = "red"
land_color = "green"

farm  [ fillcolor=land_color]
barn  [ fillcolor=building_color]
house  [ fillcolor=building_color]

}

So I can change building color once without having to go to each node. Is this possible?

Answer 1

You can define default values in order to avoid repetition:

digraph g{
   node[fillcolor=red];
   barn;
   house;
   ...
   node[fillcolor=green];
   farm;
   ...

   edge[color=red];
   barn -> house;
   edge[color=green];
   barn --> farm;
   house --> farm;
}

Real variables are not supported.

---

A more complex workaround would be to use gvpr - graph pattern scanning and processing language.

gvpr reads and outputs graph and allows to add and modify graphs, nodes and attributes.

You could for example store custom information in the comment attribute and have your script act based on the content of this attribute.

This and this SO answer contain examples of gvpr scripts.