1. An adaptable and extensible retail interface system comprising: a programmable state machine; and XML files to establish mappings and operation rules for the programmable state machine wherein the programmable state machine receives a message from a retail application and provides emulated outputs as necessary for compatible communication with a point of sale (POS) application having one or more incompatibilities preventing direct communication of the message from the retail application to the POS application and correct operation in response to the message.