[anderspitman]

Would the constraints really have to be all that intuitive? I imagine it basically being simple line and shape primitives. For example if I drag a vertex to a new location, all that would need to change in the textual representation is the position of the vertex and and edges pointing to or away from it. Obviously these would be floating point values, which isn't ideal readability wise, but should be workable. d3 sort of works like this: you can drag nodes around and the changes are reflected in the DOM. I just want something more human readable than HTML/XML. Never heard of Tom Sawyer Software. Is that your employer?

[MurrayHill1980]

No, but I have respect for their work. I'm in the graphviz project. You might take a look at Tim Dwyer's WebCola, http://marvl.infotech.monash.edu/webcola/ which is not quite what you want, but seems closer and may be a plugin replacement for D3 force layout.