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This report documents the program and the outcomes of Dagstuhl Seminar 23341 "Functionally Safe Multi-Core Systems". The seminar took place at a time when there is significant debate and disagreement in both academia and industry on how future safety-critical systems can be developed, certified, and deployed. This process is increasingly complex, as on the one hand, modern systems must provide more services while, on the other hand, analysing such systems becomes significantly more challenging in a multi-core scenario than it was in the single-core era. It is therefore a vital question to determine how the same level of certainty can be provided in the future. The seminar brought together experts from academia and industry for the three major layers involved in safety-critical systems: application, middleware, and platform. They discussed the different perspectives, which problems are deemed specifically important, and potential solutions. One main focus when organizing the seminar was to not only present the different positions but also to provide space for lengthy discussion and disagreement.

Geotechnically massive strata behave as strong units, rather than the geologically massive description which describes the sedimentary formation. The consequence of such geotechnically massive units to mining is a series of problems associated with these units failing to break up into small blocks. This paper deals with the determination of what constitutes geotechnically massive strata. This is essentially a function of the geology and the mechanical properties of the geological stratigraphic units that need to be combined into geotechnical units. The mechanical properties depend on the rock itself and on the structure in the form of joints and faults. The importance of anisotropic rock behaviour cannot be underestimated and neither can the variations in geology. Structural plate and beam analysis is presented as a method to determine where and at what span the initial fall and subsequent goaf falls will take place. While this is elastic analysis, it should be appreciated that the stronger rocks which lead to massive strata conditions will behave more elastically, and therefore this method of analysis is considered justified in most cases. This approach is considered to be far more usable and reliable than complex numerical analysis, which generally lacks the range of real rock behaviour as a fundamental input and is frequently uncheckable. The use of these established analytical techniques lends confidence to the solutions derived from their use. The pre-existing stresses are important as they will control initial goaf formation. Dynamic support loading is considered as is preconditioning to break massive units down so that they break in smaller blocks.

Conventional mixed-criticality systems (MCS)s are designed to terminate the execution of less critical tasks in exceptional situations so that the timing properties of more critical tasks can be preserved. Such a strategy can be controversial and has proven difficult to implement in practice, as it can lead to hazards and reduced functionality due to the absence of the discarded tasks. To mitigate this issue, the imprecise mixed-critically system model (IMCS) has been proposed. In such a model, instead of completely dropping less-critical tasks, these tasks are executed as much as possible through the use of decreased computation precision. Although IMCS could effectively improve the survivability of the less-critical tasks, it also introduces three key drawbacks - run-time computation errors, real-time performance degradation, and lack of flexibility. In this paper, we present a novel IMCS framework, which can (i) mitigate the computation errors caused by imprecise computation; (ii) achieve real-time performance near to that of a conventional MCS; (iii) enhance system-level throughput; and (iv) provide flexibility for run-time configuration. We describe the design details of HIART-MCS, and then present the corresponding theoretical analysis and optimisation method for its run-time configuration. Finally, HIART-MCS is evaluated against other MCS frameworks using a variety of experimental metrics.

All systems rely on inputs and outputs (I/Os) to perceive and interact with their surroundings. In safety-critical systems, it is important to guarantee both the performance and time-predictability of I/O operations. However, with the continued growth of architectural complexity in modern safety-critical systems, satisfying such real-time requirements has become increasingly challenging due to complex I/O transaction paths and extensive hardware contention. In this paper, we present a new NoC-based Predictable I/O system framework (NPRC-I/O) which reduces this contention and ensures the performance and timepredictability of I/O operations. Specifically, NPRC-I/O contains a programmable I/O command controller (NPRC-CC) and a runtime reconfigurable NoC (RNoC), which provides the capability to adjust I/O transaction paths at run-time. Using this flexibility, we construct an end-to-end transmission latency analysis and an optimisation engine that produces configurations for NPRCI/ O and the I/O traffic in a given system. The constructed analysis and optimisation engine guarantee the timing of all hard realtime traffic while reducing the deadline misses of soft real-time traffic and overall transmission latency.

Coal measure rocks tend to have anisotropic and elastically non-linear behaviour. Understanding this is a key to understanding strata behaviour in coal mines. This paper discusses which properties matter and how they can be measured. Some new test methods are introduced. The paper also discusses the relevance of geophysics in determining these properties.

This paper categorises the different types of coal bursts and gas outbursts in terms of their mechanisms. It is considered to be essentially impossible to predict when one of these events may occur. However, it is possible in many of the cases to predict the velocity of ejection and hence the distance with which particles may travel including bouncing and rolling and sliding. Keeping beyond this stand-off distance ensures the safety of workers from impact. Where gassy fault gouge exists there is no such safe distance. The material involved may be ejected in the form of a turbulent flow which has been described as a coal storm and which can travel great distances. This also involves large amounts of gas with the inherent problems of explosive mixtures. Locating, and determining the size of such geological features is therefore of great importance. Methods of doing this are discussed.

Longwall mining of coal below massive strata now has a 50 year history, and much of it has been problematic. For the first 30 years, there was much experimentation, with some successes, and many failures due to lack of understanding about how such massive strata behaves during caving, and how this differs from the more conventional and successful longwall mining beneath softer strata, which caves readily. This has been compounded over the last 20 years as mines extract wider faces and thicker seams in a single pass, often at quite shallow depths. Today, China is leading the way with thick seam longwalls under massive strata in shallow conditions, though not without problems. Determination of the required capacity for longwall roof supports in such conditions is still not adequately understood, and overloading of supports remains a common problem in modern mines. The authors’ view is that mathematical modelling to determine support requirements can only succeed if the model reflects real observed behaviour in such conditions. There is an extensive body of technical literature documenting observations of what actually happens. This paper draws on past experience in many different countries to categorise common themes, and then proposes in simple forms the basis for real behaviour. Future modelling should be advanced on this basis. Such models need to incorporate a combination of multiple failure modes, including tensile, bending and shear, which may produce large rock blocks. These may move laterally, vertically, or in rotation depending on the loads which act upon them. Large blocks may impose substantial loading on the face, the powered supports or on the gateroad pillars. The problems associated with large block formation may be mitigated by preconditioning to break up the massive strata before problems occur, so that manageable blocks are formed. In the United States of America and Australia, the focus has been on hydraulic fracturing. In Europe, China and South A

This paper reviews the need for flow monitoring in gas drainage and the flowmeters that are available to do this. As suitable flowmeters that are capable of dealing with gas, water and particulate matter do not exist work has been done to adapt ball valves for this purpose. They have been found to fill the function admirably and with a combined manometer and pressure sensor can provide flow ranges in excess of 100:1. They can also be left wide open to avoid blockage when not being used for measurement.

The sedimentary rock that comprises coal measures has quite nonlinear, elastic, stress – strain characteristics. It is also affected by the fluid pressure within it. The fluids act in two quite separate ways. The first way in which fluid acts is in a poroelastic manner while the second is within fractures. These effects are important in rock behaviour, extending from the deformation around a roadway to failure within an outburst. This paper presents the results of detailed laboratory studies into coal and sedimentary rock properties. It relates these to the real situations seen in mining.