A wide-spectrum language for verification of programs on weak memory models

Modern processors deploy a variety of weak memory models, which for efficiency reasons may (appear to) execute instructions in an order different to that specified by the program text. The consequences of instruction reordering can be complex and subtle, and can impact on ensuring correctness. Previous work on the semantics of weak memory models has focussed on the behaviour of assembler-level programs. In this paper we utilise that work to extract some general principles underlying instruction reordering, and apply those principles to a wide-spectrum language encompassing abstract data types as well as low-level assembler code. The goal is to support reasoning about implementations of data structures for modern processors with respect to an abstract specification. Specifically, we define an operational semantics, from which we derive some properties of program refinement, and encode the semantics in the rewriting engine Maude as a model-checking tool. The tool is used to validate the semantics against the behaviour of a set of litmus tests (small assembler programs) run on hardware, and also to model check implementations of data structures from the literature against their abstract specifications

On coalgebras with internal moves

In the first part of the paper we recall the coalgebraic approach to handling the so-called invisible transitions that appear in different state-based systems semantics. We claim that these transitions are always part of the unit of a certain monad. Hence, coalgebras with internal moves are exactly coalgebras over a monadic type. The rest of the paper is devoted to supporting our claim by studying two important behavioural equivalences for state-based systems with internal moves, namely: weak bisimulation and trace semantics. We continue our research on weak bisimulations for coalgebras over order enriched monads. The key notions used in this paper and proposed by us in our previous work are the notions of an order saturation monad and a saturator. A saturator operator can be intuitively understood as a reflexive, transitive closure operator. There are two approaches towards defining saturators for coalgebras with internal moves. Here, we give necessary conditions for them to yield the same notion of weak bisimulation. Finally, we propose a definition of trace semantics for coalgebras with silent moves via a uniform fixed point operator. We compare strong and weak bisimilation together with trace semantics for coalgebras with internal steps.Comment: Article: 23 pages, Appendix: 3 page

A qualitative evaluation of Southwark Council’s public health response to mitigating the mental health impact of the 2017 London bridge and borough market terror attack

Background Over recent years there have been several major terror attacks in cities across Europe. These attacks result in deaths, physical injuries, and pose long-term threats to mental health and wellbeing of large populations. Although psychologists have completed important work on mental health responses to disaster exposure including terrorist attacks, the mental health impacts of such attacks have been comparatively less examined in academic literature than the acute health response to physical injuries. This paper reflects on Southwark Council’s pioneering public mental health response to the June 2017 terror attack at London Bridge and Borough Market. It aims to explore perceptions of the mental health impact of the incident by those living and working in the borough. Methods A rapid qualitative evaluation informed by the logic underpinning Southwark Council’s response was conducted. Seven formative interviews were undertaken with individuals involved in the response planning and/or delivery, enabling the evaluation team to establish the response’s theoretical basis. Subsequently, nineteen semi-structured interviews with consenting Council employees, residents, business owners, and workers from the Borough were conducted to understand perceived mental health impacts of the attack and the success of the Council response. Thematic analysis of transcribed interviews was undertaken to evaluate the extent to which the response was implemented successfully. Results Participants reported feeling the attack had a wide-reaching negative impact on the mental health of residents, those working in the borough and visitors who witnessed the attack. Delivering the response was a challenge and response visibility within the community was limited. Participants suggested a comprehensive systematic approach to health needs assessment informed by knowledge and relationships of key Council workers and community stakeholders is imperative when responding to terrorist incidents. Improved communication and working relationships between statutory organisations and community stakeholders would ensure community groups are better supported. Prioritising mental health needs of terror attack responders to mitigate persisting negative impacts was highlighted. Conclusions This article highlights a potential public health approach and need for developing robust practical guidance in the aftermath of terror attacks. This approach has already influenced the response to the Christchurch mosque shooting in 2019.Guy’s and St Thomas’ Charity

Applications of Fair Testing

In this paper we present the application of the fair testing pre-order, introduced in a previous paper, to the specification and analysis of distributed systems. This pre-order combines some features of the standard testing pre-orders, viz. the possibility to refine a specification by the resolution of nondeterminism, with a powerful feature of standard observation congruence, viz. the fair abstraction from divergences. Moreover, it is a pre-congruence with respect to all standard process-algebraic combinators, thus allowing for the standard algebraic proof techniques by substitution and rewriting. In this paper we will demonstrate advantages of the fair testing pre-order by the application to a number of examples, including a scheduling problem, a version of the Alternating Bit-protocol, and fair communication channels

Patients’ and clinicians’ views on the optimum schedules for self-monitoring of blood pressure

This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by the Royal College of General Practitioners.Background Self-monitoring of blood pressure is common but guidance on how it should be carried out varies and it is currently unclear how such guidance is viewed. Aim To explore patients' and health care professionals' (HCPs) views and experiences of the use of different self-monitoring regimes, to determine what is acceptable and feasible and to inform future recommendations. Design and Setting Thirteen focus groups plus four HCP interviews were held, total of 66 participants (41 patients, 25 HCPs) from primary and secondary care with and without experience of self-monitoring. Method Both standard and shortened self-monitoring protocols were considered. Focus groups and interviews were recorded, transcribed verbatim and analysed by constant comparative method. Results Patients generally supported structured schedules but with sufficient flexibility to allow adaptation to individual routine. They preferred a shorter (3-day) schedule to longer (7-day) regimes. Whilst HCPs could describe benefits for patients of using a schedule, they were reluctant to recommend a specific schedule. Concerns surrounded the use of different schedules for diagnosis and subsequent monitoring. Appropriate education was seen as vital by all participants to enable a self-monitoring schedule to be followed at home. Conclusions There is not a 'one size fits all approach' to developing the optimum protocol from the perspective of users and those implementing it. An approach whereby patients are asked to complete the minimum number of readings required for accurate BP estimation in a flexible manner seems most likely to succeed. Informative advice and guidance should incorporate such flexibility for patients and professionals alike.This study was independent research commissioned by the National Institute for Health Research (NIHR) as part of a Programme Grant for Applied Research “Optimising the diagnosis and management of hypertension in primary care through self-monitoring of blood pressure” (RP-PG-1209-10051). RJM receives funding from an NIHR Professorship (NIHR-RP-02-12-015). FDRH is part funded by the National Institute for Health Research (NIHR) School for Primary Care Research (SPCR), NIHR Oxford Biomedical Research Centre (BRC), NIHR Oxford Collaboration for Leadership in Applied Health Research (CLAHRC), and is supported by Harris Manchester College, Oxford. Sheila Greenfield is supported by the NIHR CLAHRC West Midlands initiative

Dynamic Locomotor Capabilities Revealed by Early Dinosaur Trackmakers from Southern Africa

BACKGROUND: A new investigation of the sedimentology and ichnology of the Early Jurassic Moyeni tracksite in Lesotho, southern Africa has yielded new insights into the behavior and locomotor dynamics of early dinosaurs. METHODOLOGY/PRINCIPAL FINDINGS: The tracksite is an ancient point bar preserving a heterogeneous substrate of varied consistency and inclination that includes a ripple-marked riverbed, a bar slope, and a stable algal-matted bar top surface. Several basal ornithischian dinosaurs and a single theropod dinosaur crossed its surface within days or perhaps weeks of one another, but responded to substrate heterogeneity differently. Whereas the theropod trackmaker accommodated sloping and slippery surfaces by gripping the substrate with its pedal claws, the basal ornithischian trackmakers adjusted to the terrain by changing between quadrupedal and bipedal stance, wide and narrow gauge limb support (abduction range = 31 degrees ), and plantigrade and digitigrade foot posture. CONCLUSIONS/SIGNIFICANCE: The locomotor adjustments coincide with changes in substrate consistency along the trackway and appear to reflect 'real time' responses to a complex terrain. It is proposed that these responses foreshadow important locomotor transformations characterizing the later evolution of the two main dinosaur lineages. Ornithischians, which shifted from bipedal to quadrupedal posture at least three times in their evolutionary history, are shown to have been capable of adopting both postures early in their evolutionary history. The substrate-gripping behavior demonstrated by the early theropod, in turn, is consistent with the hypothesized function of pedal claws in bird ancestors