In [4], Freuderdefines several types of interchangeability to capture the equivalenceamongthe valuesof a variable in a discrete constraint satisfaction problem(CSP), and provides a procedure for computing onetype of local interchangeability.In this paper, we first extendthis procedurefor computinga weakform of local interchangeability. Second,weshowthat the modifiedprocedurecanbe used to generate a conjunctive decompositionof the CSPby localizing, in the CSP,independentsubproblems.Third, for the case of constraints of mutualexclusion, weshowthat locally interchangeablevaluescan be computedin a straightforward manner,and that the only possible type of local interchangeabilityis the onethat induceslocally independentsubproblems.Finally, wegive hints on howto exploit these results in practice, establish a lattice that relates sometypes of interchangeability, andidentify directions for future research.
Berthe Y. Choueiry, Guevara Noubir