Decomposition of the NVALUE constraint
  We study decompositions of NVALUE, a global constraint that can be used to
model a wide range of problems where values need to be counted. Whilst
decomposition typically hinders propagation, we identify one decomposition that
maintains a global view as enforcing bound consistency on the decomposition
achieves bound consistency on the original global NVALUE constraint. Such
decompositions offer the prospect for advanced solving techniques like nogood
learning and impact based branching heuristics. They may also help SAT and IP
solvers take advantage of the propagation of global constraints.
