Auxiliary varialbes

Pattern name AuxiliaryVars.
Context A basic model in which two or more constraints repeat expressions.
Problem Insufficient propagation between these constraints.
Forces Overhead of introducing additional variables.
Solution Introduce auxiliary variables for the repeated expressions.
Example Golomb ruler problem, prob006 in CSPLib.
References Using Auxiliary Variables and Implied Constraints to Model Non-binary Problems (ps, pdf)
Barbara Smith, Kostas Stergiou and Toby Walsh, Proceedings of AAAI-2000, 2000.