Standards for the design of real time systems
M Blackman · ITNOW · 1976
For the purposes of this discussion the term real time will be used to describe any transaction driven production application, that is one whose processing is triggered by single events, usually from keyboard terminals. This definition is intended to include simple inquiry systems, online data capture systems and commercial file updating systems and to exclude such uses as online program development not normally the concern of commercial analysts and programmers. In such a system the demand for processing must be satisfied quickly because someone is waiting at a terminal for a response. The key characteristics are that the system is conversational and that it is serving a commercial or administrative purpose. Any scheme of documentation and methods for such applications must emphasise certain requirements. These requirements are derived from the proximity of the user to the system. A batch system imposes a number of shields between the user and his system: data preparation, job control, job assembly and operations. These shields reduce the impact on the user of any defects of system design except in such matters as the utility of the reports produced by the system. In real time there is no such barrier. The user interacts with the system, is aware of inefficiencies in design, of poor testing and unreliable hardware because he experiences them. A real time system design method must therefore emphasise