A method and system for a client application (1) to request a data item from an access server (3) in a computer controlled control system. The control system includes objects and a plurality of access servers, which said objects represent various entities that have a defined functional meaning in the control system. Each access server, such as an OPC server, may provide access to one or more real-time data, historical data, and alarm and event data items. In an embodiment the method provides means, which enables the Access Service Handler (2) component, by querying a said object, to obtain a reference for a desired data item, to find out which access server handles the said data item. The Access Service handler then makes request to the identified access server.