Timing extensions to structured analysis for real time systems

Abstract

The Structured Analysis method has been modified and extended to incorporate techniques for accurately estimating the execution time for real time systems during the analysis and/or design phases. This estimating technique enables the software engineer to incorporate the effects of external hardware devices, concurrency of processing, synchronization, priorities, interrupts, and other factors traditionally excluded from consideration by the Stnrcntred Methods. The methods which have been incorporated into Structured Analysis in order to address real time systems include an object oriented view of the relationship of priority to data items, formal means of evaluating system partitioning, and a specialized form of notation. Best, worst, and nominal times, blockage probabilities, and the effects of various resource allocation strategies can be evaluated in a timely and cost effective manner using this revised form of these methods. These extensions support safety and hazard analyses by cataloguing all possible modes of operation of the system being modeled. The application of this methodology is supported by and demonstrated on a software tool. This extension of Structured Analysis is referred to as HRT/DM (Hard Real Time Development Method).