Data processing system

A data processing system is provided comprising a processing unit (4, Fig. 2), a memory unit for storing a plurality of procedures, and a terminal unit comprising display means (2) for displaying an information form (Fig. 3) to a terminal user, said information form comprising a plurality of display tiles, and input means (5) for enabling said terminal user to enter an event into said system in the form of data or a command regarding said information form by selecting a portion of said form comprising at least one of said display tiles. A method is described for processing said event by at least one of said procedures and for providing to said terminal user a visual indication thereof. The procedures are represented by function graphs (500, Fig. 12A), each function graph including a plurality of nodes (501-505), including an initialization node (501) for handling initialization functions, a dialog node (502-504) for handling processing functions, and an exit node (505) for handling exit functions. The nodes may import and export variables, and the function graph includes an import table (Fig. 10) for specifying the import variables for each of the nodes and an export table (Fig. 10) for specifying the export variables for each of the nodes. The nodes are loosely coupled and need not be aware of the import/export variables for other nodes.