One lesson learned from practical constraint solving applications is that

  constraints are often heterogeneous. Solving such constraints requires a

  collaboration of constraint solvers. In this paper, we introduce a methodology

  for the tight integration of CHR constraint programs into one such program.

  \chr\ is a high-level rule-based language for writing constraint solvers and

  reasoning systems.  A constraint solver is well-behaved if it is terminating

  and confluent. When merging constraint solvers, this property may be

  lost. Based on previous results on CHR program analysis and transformation we

  show how to utilize completion to regain well-behavedness. We identify a class

  of solvers whose union is always confluent and we show that for preserving

  termination such a class is hard to find.

    

    The merged and completed constraint solvers may contain redundant

    rules. Utilizing the notion of operational equivalence, which is

    decidable for well-behaved CHR programs, we present a method to

    detect redundant rules in a CHR program.