If you are using some SPARQL-in-SQL system then you must be customizing a lot, at least the SQL queries. It is hard to help since all that is not project code. Are you so sure the queries being executed work? Have you looked at log output? What code version? No there should be no hidden exceptions - but some are logged not thrown where not possible. I would just debug, that will show the issue quickly. On Nov 4, 2009 5:04 PM, "Mirko" wrote: Hi, I have problems with the GenericJDBCDataModel. For me, the functions getUsers() and getItems() return nothing, although the SQL queries used in the functions definitely do return results. All other functions in the DataModel work as expected. The results of the queries used in getUsers() and getItems() look as follows: SQL result for GenericJDBCDataModel.GET_ITEMS_SQL_KEY: item_id ------------ itemID_A itemID_B itemID_C itemID_D itemID_E ... SQL result for GenericJDBCDataModel.GET_USERS_SQL_KEY item_id callret-1 user_id ---------------------------------------------- itemID_A 1 userID_X itemID_B 1 userID_Y itemID_C 1 userID_Z ... I think these results should be correct (Preferences are always 1 in my data). But the Iterables returned by both functions seem to be empty: GenericJDBCDataModel dm = new GenericJDBCDataModel(props); for ( Item item : dm.getItems()){ System.out.println(item.getID()); //Never reached } for ( User user : dm.getUsers()){ System.out.println(user.getID()); //Never reached } I should note that I query an OpenLink Virtuoso RDF store, which uses SPARQL queries enclosed in SQL queries. That means that 'columns' and 'tables' , and thus the variables DEFAULT_PREFERENCE_TABLE, DEFAULT_USER_ID_COLUMN, DEFAULT_ITEM_ID_COLUMN and DEFAULT_PREFERENCE_COLUMN of AbstractJDBCDataModel don't have any meaning. But as I understand the code, they are not required when using the GenericJDBCDataModel. Is it possible that some exception is thrown 'silently' in the AbstractJDBCDataModel? I have no idea where to look for the prob, so thanks for any hints.... Regards, Mirko