code: public List<String> getServicesIDByCategory(String category) {
  		Set<String> servicesID = services.keySet();
  		Iterator<String> it = servicesID.iterator();
  		List<String> ids = new ArrayList<String>();
  
  		if (category == null) {
  			return ids;
  		}
  
  		String key;
  		while (it.hasNext()) {
  			key = it.next();
  			DescribeService service = services.get(key);
  			if (service.containsCategory(category)) {
  				ids.add(key);
  			}
  		}
  
  		return ids;
  	}
docs: Iterates the list of registered services and for those that support the
  category passed as a parameter return their ID
  
  @param category
  @return