An interface (1) interfaces between front-end systems and back-end systems (10, 11, 12) in a manner whereby their communication formats may be different and they may change. There is an engine (2), a node layer of nodes (3, 4) and a utility layer of utilities (5, 6, 7). An engine (2) has an engine object which instantiates processor, script loader, parser, and script builder objects. An XML script contains a process map for associating incoming messages from the front-end systems with nodes (3, 4). The association is determined by the parser object. The engine has no specific business logic, this logic being represented by the nodes. The nodes expose their business logic capabilities to the engine (2), allowing it to dynamically maintain its process map. Messages are routed to the relevant nodes, which communicate with the relevant back-end systems via the utilities (5, 6, 7). Messages are passed between the nodes and the engine objects using a hashtable associating keys with values.