Martin Kraus: Direct Manipulation of Parametrized Graphics
  What is Direct Manipulation of Parametrized Graphics?

  Related work:
many constraint solving systems
Cabri-geometry (Windows, MacOS, Java; only geometry)
The Geometer's Sketchpad (Windows, MacOS, Java; only geometry)
Cinderella (Java, only geometry)
George W. Fitzmaurice and Bill Buxton, HMDs, Caves & Chameleon, Computer Graphics 32(4), 1998
Chikara Miyaji, Interactive Graphics Using MathLink, IMS 1999