UW DeltaBlue Constraint Solver

(Last updated 30 June 1998)

DeltaBlue is an efficient, incremental local propagation constraint solver. Like most local propagation algorithms, it cannot accomodate cyclic constraints. Our current research is focussed primarily on constraint solvers that do not have this restriction, and we have now released the Cassowary Constraint Solving Toolkit for linear arithmetic constraints.

However, DeltaBlue may still be of interest to some researchers, since it is able to handle constraints over arbitrary domains. Here are links to a comprehensive paper on DeltaBlue, and a code archive:

• Michael Sannella, John Maloney, Bjorn Freeman-Benson, and Alan Borning, "Multi-way versus One-way Constraints in User Interfaces: Experience with the DeltaBlue Algorithm", Software--Practice and Experience, Vol. 23 No. 5, (May 1993), pages 529-566.
• DeltaBlue code archive (Versions in C, Smalltalk, and Lisp. Please note that we are no longer supporting this code, however.)

A current research topic is how to integrate a DeltaBlue-like local propagation solver with Cassowary. If this effort is successful, we will include this code in future versions of Cassowary.