conceptNodeIndex = new ConcurrentHashMap<String, Node>();
Node top = null;
Node bottom = null;
IConceptSet processed = new FastConceptHashSet();
Set<Node> nodeSet = new HashSet<Node>();
for(int key : equiv.keySet()) {
if(processed.contains(key)) continue;
IConceptSet equivs = equiv.get(key);
processed.addAll(equivs);
Node n = new Node();
for(IntIterator it = equivs.iterator(); it.hasNext(); ) {
int val = it.next();
String tval = factory.lookupConceptId(val).toString();