public void checkBindings(Expression exp) {
HashMap<Integer,Link> declared = new HashMap<Integer,Link>();
List<Integer> used = new ArrayList<Integer>();
for (Agent a : exp.getAgents()) {
for (Site site : a.getSites()) {
Link link = site.getLink();
if (link != null && link.getC() == null){
Integer n = link.getN();
if (used.contains(n)){
error("The binding indicator:"+n+" has been used more than twice",link, KappaPackage.LINK__N);
} else {
if (declared.keySet().contains(n)){
declared.remove(n);