Constraints are an important enabling technology for interactive graphics applications.
However, today's constraint-based systems are plagued by several limitations, and constraints have yet to live up to their potential. Constraints allow you to specify locations in your drawing declaratively. The constraints are maintained whenever part of the picture is changed, so constraints make it easier to maintain a picture in the face of modifications. The system demonstrates that fast constraint solving is possible with a highly extensible, fully declarative constraint language. More recently, he has been working on the Vesta software configuration management system.