Approximating Partial Interchangeability in CSP Solutions

The concept of interchangeability characterizes the possibilities for making local changes to CSP solutions. Often, interchangeability is only partial and also requires changing values assigned to other variables, called the dependent set. As partial interchangeability (PI) can only be computed by solving the whole problem, it needs to be approximated. We introduce the new concept of neighborhood tuple interchangeability (NTI) and show that it correctly approximates partial interchangeability (PI). We propose an algorithm for computing smallest dependent sets for NTI.