title: Programmatically draw block diagram in d3.js or graphviz or similar
body: <p>I would like to programmatically draw block diagrams of the type used in control theory and systems analysis. See for example <a href="http://en.wikibooks.org/wiki/Control_Systems/Block_Diagrams" rel="nofollow noreferrer">http://en.wikibooks.org/wiki/Control_Systems/Block_Diagrams</a> .</p>
  
  <p>The best tool I have found is <a href="http://blockdiag.com/" rel="nofollow noreferrer">http://blockdiag.com/</a> however the edge labelling is not very nice: I require labels not in boxes and to the side of the edges.</p>
  
  <p>To get an idea of the problem, I am getting (from blockdiag):
     <a href="http://interactive.blockdiag.com/?compression=deflate&amp;src=eJyr5lJQcFTQtVNwAhHO1kAuGIC5LgrROYlJqTm2SklKsXApF4hymFQiSKoWABD8D8U" rel="nofollow noreferrer">http://interactive.blockdiag.com/?compression=deflate&amp;src=eJyr5lJQcFTQtVNwAhHO1kAuGIC5LgrROYlJqTm2SklKsXApF4hymFQiSKoWABD8D8U</a></p>
  
  <p>related qns:
      <a href="https://stackoverflow.com/questions/6422603/circuit-block-diagram-drawing/12205193#12205193">circuit/block-diagram drawing</a></p>