I would like to programmatically draw block diagrams of the type used in control theory and systems analysis. See for example http://en.wikibooks.org/wiki/Control_Systems/Block_Diagrams .
The best tool I have found is http://blockdiag.com/ however the edge labelling is not very nice: I require labels not in boxes and to the side of the edges.
To get an idea of the problem, I am getting (from blockdiag): http://interactive.blockdiag.com/?compression=deflate&src=eJyr5lJQcFTQtVNwAhHO1kAuGIC5LgrROYlJqTm2SklKsXApF4hymFQiSKoWABD8D8U
related qns: circuit/block-diagram drawing