A method for processing data in a data processing system (1) which includes a number of data processing units (2), and operator and observation units (4), which are interconnected by way of a data transmission unit (6), whereby a respective data processing program (8) with corresponding function modules (FB1 to FBn) and data modules (DB 1 to DBn) is implemented in the data processing units (2). At least one identifier (K, KE, KI) for the function modules and data modules is stored in a respective conversion table (10) belonging to each data processing unit (2). When an external data processing unit (2) accesses a data module (DB1 to DBn) and/or a function module (FB1 to FBn) of another data processing unit (2), a conversion table (10) mediates by using an external identifier (KE) that characterizes the access and verifies whether a matching internal identifier (KI) is stored for the particular external identifier (KE).