public ERDBuilder() throws MainException {
		dbAccess            = DBAccess.getInstance();
		tableNames          = dbAccess.getTableNames();
		entityTypes         = new HashMap<String, ErdNode>();
		relationshipTypes   = new HashMap<String, ErdNode>(); 
		cycles			    = new ArrayList<List<String>>();
		relationshipInCycle = new ArrayList<List<String>>();

	}