Performance Analysis and Functional Verification of the Stop-and-Wait Protocol in HOL

Real-time systems usually involve a subtle interaction of a number of distributed components and have a high degree of parallelism, which makes their performance analysis quite complex. Thus, traditional techniques, such as simulation, or the state-based formal methods usually fail to produce reasonable results. In this paper, we propose to use higher-order-logic (HOL) theorem proving for the performance analysis of real-time systems. The idea is to formalize the real-time system as a logical conjunction of HOL predicates, whereas each one of these predicates define an autonomous component or process of the given real-time system. The random or unpredictable behavior found in these components is modeled as random variables. This formal specification can then be used in a HOL theorem prover to reason about both functional and performance related properties of the given real-time system. In order to illustrate the practical effectiveness of our approach, we present the analysis of the Stop-and-Wait protocol, which is a classical example of real-time systems. The functional correctness of the protocol is verified by proving that the protocol ensures reliable data transfers. Whereas, the average message delay relation is verified in HOL for the sake of performance analysis. The paper includes the protocol’s formalization details along with the HOL proof sketches for the major theorems

The rite way

There is a way to help students to develop into healthy young men and women - by creating meaningful rites of passage. The health and well-being of boys, as well as girls, are matters rarely off the educational agenda, and substantial thought and resources have been devoted to them over the years, yet educators still appear to be failing to meet the needs of children, particularly boys, in the current education system. More than that, educators appear to be failing at a time when the burden of responsibility for the emotional and social education of children is shifting from the family to the school. Worse still for boys, Western society has lost some of the most significant emotional and social educational tools: initiation and rites of passage. The authors describe a program they created called the Rite Journey, in which the role of men is to act as guides for boys searching for what it means to be a man, and the best men they can become. The program is based on the seven steps of a hero\u27s journey; these seven stages frame the ceremonies and celebrations that occur throughout the year. Each of these ceremonies or celebrations acknowledges the passage, the emphasis being to honour the process and the boys\u27 experiences as they undertake the passage. A version of the Rite Journey has now also been created for girls. [Author abstract, ed

Monitoring the age of vehicle shock absorbers

Shock absorber performance is critical to the operation of military vehicles. The Australian Army is interested in implementing health and usage monitoring systems for improved maintenance and fleet management. Shock absorbers typically break down by the failure of the seal where the rod shaft enters the main body, or the seal at the end of the piston within the body. There are few practical options for monitoring the condition of shock absorbers due to harsh operating environments (temperature, dirt, shock loading and continual vibration). Instead of monitoring the change in dynamic performance of a suspension system, it is proposed that the age of a shock absorber can be estimated by measuring the cumulative work done using a calorimetry method involving temperature sensors. This paper describes a simplified thermo-mechanical model that can be used to estimate the cumulative work done by a shock absorber, which is indicative of its age.Carl Q. Howard, Nataliia Sergiienko, Guy Gallasc