An activity may only require one single resource from a set of alternative resources during its execution, without specifying which one. We declare the resource constraints in the same manner as in previous examples, except that the activities masonry and plumbing require one of the workers in our alternative resource set (workers[1] or workers[2]).

  /* POST THE RESOURCE CONSTRAINTS. */ 
  model.add(carpentry.requires(workers[0]));
  model.add(ceiling.requires(workers[0]));
  model.add(roofing.requires(workers[0]));
  model.add(windows.requires(workers[0]));
  model.add(facade.requires(workers[0]));
 
  model.add(masonry.requires(workers[1]));
 
  model.add(plumbing.requires(workers[2]));
 
  model.add(garden.requires(workers[3]));
  model.add(painting.requires(workers[3]));
  model.add(moving.requires(workers[3]));