opl model of the worker allocation problem

An OPL model of the Worker Allocation Problem

range Boolean 0..1;
in nbWorkers = ...;
range Workers 1..nbWorkers;
enum Tasks ...;
{Workers} qualified[Tasks] = ...;
int cost[Workers] = ...;

var Boolean hire[Workers];
minimize
     sum(c in Workers) cost[c]*hire[c]
subject to
     forall(j in Tasks)
        sum(c in qualified[j]) hire[c] >= 1;

{Workers} crew = {c| c in Workers: hire[c] = 1};
display crew;

this model appears in: Pascal Van Hentenryck. The OPL Optimization Programming Language.
MIT Press, January 1999.