public String getPastString() {
		String past_string = (String) cache.get("past_string");
		if (past_string != null)
			return past_string;
		Entity past_entity = null;
		DatastoreService datastore = DatastoreServiceFactory
				.getDatastoreService();
		try {
			past_entity = datastore.get(KeyFactory.createKey("past_string",
					"onlyOne"));
		} catch (EntityNotFoundException e) {
		}
		past_string = ((Text) past_entity.getProperty("text")).getValue();
		return past_string;
	}