Generalizations of the global cardinality constraint for hierarchical resources

We propose generalizations of the global cardinality constraint (gcc) in which a partition of the variables is given. In the context of resource allocation problems, such constraints allow the expression of requirements, in terms of lower and upper bounds, for resources with different capabilities. Alternate models using gcc's are shown to be weaker. We present filtering algorithms based on flow theory that achieve domain consistency and give experimental evidence of the usefulness of such constraints. We consider an optimization version of the constraints and discuss its relationship with the cost_gcc.