A stable non-interleaving early operational semantics for the pi-calculus

We give the first non-interleaving early operational semantics for the pi-calculus which generalises the standard interleaving semantics and unfolds to the stable model of prime event structures. Our starting point is the non-interleaving semantics given for CCS by Mukund and Nielsen, where the so-called structural (prefixing or subject) causality and events are defined from a notion of locations derived from the syntactic structure of the process terms. We conservatively extend this semantics with a notion of extruder histories, from which we infer the so-called link (name or object) causality and events introduced by the dynamic communication topology of the pi-calculus. We prove that the semantics generalises both the standard interleaving early semantics for the pi-calculus and the non-interleaving semantics for CCS. In particular, it gives rise to a labelled asynchronous transition system unfolding to prime event structures

Relational Semantics of Non-Deterministic Dataflow

We recast dataflow in a modern categorical light using profunctors as a generalization of relations. The well known causal anomalies associated with relational semantics of indeterminate dataflow are avoided, but still we preservemuch of the intuitions of a relational model. The development fits with the view of categories of models for concurrency and the general treatment of bisimulation they provide. In particular it fits with the recent categorical formulation of feedback using traced monoidal categories. The payoffs are: (1) explicit relations to existing models and semantics, especially theusual axioms of monotone IO automata are read off from the definition of profunctors, (2) a new definition of bisimulation for dataflow, the proof of the congruence of which benefits from the preservation properties associated with open maps and (3) a treatment of higher-order dataflow as a biproduct,essentially by following the geometry of interaction programme

Capturing Smart Contract Design with DCR Graphs

Smart contracts manage blockchain assets. While smart contracts embody business processes, their platforms are not process-aware. Mainstream smart contract programming languages such as Solidity do not have explicit notions of roles, action dependencies, and time. Instead, these concepts are implemented in program code. This makes it very hard to design and analyze smart contracts. We argue that DCR graphs are a suitable formalization tool for smart contracts because they explicitly and visually capture these features. We utilize this expressiveness to show that many common high-level design patterns in smart-contract applications can be naturally modeled this way. Applying these patterns shows that DCR graphs facilitate the development and analysis of correct and reliable smart contracts by providing a clear and easy-to-understand specification

Understandability of Hybrid Process Models Using DCR Graphs

While the understandability of process models has been extensively investigated for different process modeling notations, it has not been yet broadened to cover hybrid models. This paper proposes a new research model to investigate the understandability of hybrid model representations using a variety of psycho-physiological measurements including eye tracking and galvanic skin response (GSR) together with verbal data analysis. The aim of this research is to ensure a smooth integrationof hybrid modelling technologies in public administrations by investigating the way end-users (i.e., case workers) rely on the different parts of the hybrid process model representation in DCR Graphs, i.e., the graph, the textual annotations describing the law, and the simulation tools to interpret the process model

Agents intervening against delirium in the intensive care unit (AID-ICU) - Protocol for a randomised placebo-controlled trial of haloperidol in patients with delirium in the ICU

Background Delirium among patients in the intensive care unit (ICU) is a common condition associated with increased morbidity and mortality. Haloperidol is the most frequently used pharmacologic intervention, but its use is not supported by firm evidence. Therefore, we are conducting Agents Intervening against Delirium in the Intensive Care Unit (AID‐ICU) trial to assess the benefits and harms of haloperidol for the treatment of ICU‐acquired delirium. Methods AID‐ICU is an investigator‐initiated, pragmatic, international, randomised, blinded, parallel‐group, trial allocating adult ICU patients with manifest delirium 1:1 to haloperidol or placebo. Trial participants will receive intravenous 2.5 mg haloperidol three times daily or matching placebo (isotonic saline 0.9%) if they are delirious. If needed, a maximum of 20 mg/daily haloperidol/placebo is given. An escape protocol, not including haloperidol, is part of the trial protocol. The primary outcome is days alive out of the hospital within 90 days post‐randomisation. Secondary outcomes are number of days without delirium or coma, serious adverse reactions to haloperidol, usage of escape medication, number of days alive without mechanical ventilation; mortality, health‐related quality‐of‐life and cognitive function at 1‐year follow‐up. A sample size of 1000 patients is required to detect a 7‐day improvement or worsening of the mean days alive out of the hospital, type 1 error risk of 5% and power 90%. Perspective The AID‐ICU trial is based on gold standard methodology applied to a large sample of clinically representative patients and will provide pivotal high‐quality data on the benefits and harms of haloperidol for the treatment ICU‐acquired delirium

Categorical Models for Concurrency: Independence, Fairness and Dataflow

This thesis is concerned with formal semantics and models for concurrent computational systems, that is, systems consisting of a number of parallel computing sequential systems, interacting with each other and the environment. A formal semantics gives meaning to computational systems by describing their behaviour in a mathematical model. For concurrent systems the interesting aspect of their computation is often how they interact with the environment during a computation and not in which state they terminate, indeed they may not be intended to terminate at all. For this reason they are often referred to as reactive systems, to distinguish them from traditional calculational systems, as e.g. a program calculating your income tax, for which the interesting behaviour is the answer it gives when (or if) it terminates, in other words the (possibly partial) function it computes between input and output. Church's thesis tells us that regardless of whether we choose the lambda calculus, Turing machines, or almost any modern programming language such as C or Java to describe calculational systems, we are able to describe exactly the same class of functions. However, there is no agreement on observable behaviour for concurrent reactive systems, and consequently there is no correspondent to Church's thesis. A result of this fact is that an overwhelming number of different and often competing notions of observable behaviours, primitive operations, languages and mathematical models for describing their semantics, have been proposed in the litterature on concurrency. The wor

A Fully Abstract Presheaf Semantics of SCCS with Finite Delay

We present a presheaf model for the observation of infinite as well as finite computations. We apply it to give a denotational semantics of SCCS with finite delay, in which the meanings of recursion are given by final coalgebras and meanings of finite delay by initial algebras of the process equations for delay. This can be viewed as a first step in representing fairness in presheaf semantics. We give a concrete representation of the presheaf model as a category of generalised synchronisation trees and show that it is coreflective in a category of generalised transition systems, which are a special case of the general transition systems of Hennessy and Stirling. The open map bisimulation is shown to coincide with the extended bisimulation of Hennessy and Stirling. Finally we formulate Milners operational semantics of SCCS with finite delay in terms of generalised transition systems and prove that the presheaf semantics is fully abstract with respect to extended bisimulatio