| Real-time software must satisfy response time requirements of the system in which it is embedded. Of current real-time software development methods, only rate monotonic scheduling theory offers the possibility of using system timing information during software design to provide feedback on the expected performance of the proposed design. The feedback is in the form of analytic evaluation.;This research focuses on incorporating timing information explicitly at the design stage and providing feedback, through discrete event stimulation, to the system designer. The specific context of the research is input-driven, real-time software systems that are written in Ada and that include intertask communication. The expected performance of the design is defined in terms of meeting response time requirements of I/O pairs.;The research has developed an I/O Failure Analysis Methodology (I/OFAM). I/OFAM combines performance factors, or overall system operational characteristics, with failure analysis of I/O pairs which have exceeded their required response time. I/OFAM builds on event-oriented design, an augmentation to real-time systems design that incorporates timing information into a high level model of the system called an event diagram.;I/OFAM has been automated in prototype form with a Performance and Failure Analysis Module and a User Interface. The Performance and Failure Analysis Module builds on an existing discrete event simulator, the Embedded Software Design Simulator.;The prime contribution of I/OFAM and its automation is its situation within the software design process, enabling feedback on the expected performance of a proposed design at an early stage in the software lifecycle. It provides not just performance and I/O failure statistics, but information about and insight into the reasons for these statistics. I/O failure analysis presents information about problems encountered by a failed I/O pair, their causes, possible solutions, and the impacts of adopting a solution. As appropriate, data pertaining to the feasibility of adopting a solution are also presented. Thus, I/OFAM aids the user to modify and optimize a design. I/OFAM and its automation provide for the comparison of alternative proposed designs, enabling the user to assess the effect of changes in the design as modifications are made to solve response time problems. |
