Abstract: The invention relates to a process for data exchange via a communications channel between a central unit, which processes, stores and provides data, and a data terminal device. Initially, a permanently unchanged application-independent query structure (general query structure) is stored both in the central unit and in the data terminal device, as are a small number of permanently unchanged application-independent response formats. For each application, the specific query structure is defined on the basis of the general query structure and is stored in the central unit in the form of a parameter set. As needed, the data terminal device requests from the center unit, via the communications channel, a specific query structure not yet stored in the data terminal device and receives and stores the applicable parameter set.