Causal computational complexity of distributed processes

This article studies the complexity of π-calculus processes with respect to the quantity of transitions caused by an incoming message. First, we propose a typing system for integrating Bellantoni and Cook's characterisation of polytime computable functions into Deng and Sangiorgi's typing system for termination. We then define computational complexity of distributed messages based on Degano and Priami's causal semantics, which identifies the dependency between interleaved transitions. Next, we apply a necessary syntactic flow analysis to typable processes to ensure a computational bound on the number of distributed messages. We prove that our analysis is decidable; sound in the sense that it guarantees that the total number of messages causally dependent of an input request received from the outside is bounded by a polynomial of the content of this request; and complete, meaning that each polynomial recursive function can be computed by a typable process

Embedding Session Types in HML

Recent work on the enhancement of multiparty session types with logical annotations enable the effective verification of properties on (1) the structure of the conversations, (2) the sorts of the messages, and (3) the actual values exchanged. In [3] we extend this work to enable the specification and verification of mutual effects of multiple cross-session interactions. Here we give a sound and complete embedding into the Hennessy-Milner logic to justify the expressiveness of the approach in [3] and to provide it with a logical background that will enable us to compare it with similar approaches

Monitoring Networks through Multiparty Session Types

In large-scale distributed infrastructures, applications are realised through communications among distributed components. The need for methods for assuring safe interactions in such environments is recognised, however the existing frameworks, relying on centralised verification or restricted specification methods, have limited applicability. This paper proposes a new theory of monitored π-calculus with dynamic usage of multiparty session types (MPST), offering a rigorous foundation for safety assurance of distributed components which asynchronously communicate through multiparty sessions. Our theory establishes a framework for semantically precise decentralised run-time enforcement and provides reasoning principles over monitored distributed applications, which complement existing static analysis techniques. We introduce asynchrony through the means of explicit routers and global queues, and propose novel equivalences between networks, that capture the notion of interface equivalence, i.e. equating networks offering the same services to a user. We illustrate our static–dynamic analysis system with an ATM protocol as a running example and justify our theory with results: satisfaction equivalence, local/global safety and transparency, and session fidelity

Effects as Sessions, Sessions as Effects

Effect and session type systems are two expressive behavioural type systems. The former is usually developed in the context of the lambda-calculus and its variants, the latter for the ?-calculus. In this paper we explore their relative expressive power. Firstly, we give an embedding from PCF, augmented with a parameterised effect system, into a session-typed pi-calculus (session calculus), showing that session types are powerful enough to express effects. Secondly, we give a reverse embedding, from the session calculus back into PCF, by instantiating PCF with concurrency primitives and its effect system with a session-like effect algebra; effect systems are powerful enough to express sessions. The embedding of session types into an effect system is leveraged to give a new implementation of session types in Haskell, via an effect system encoding. The correctness of this implementation follows from the second embedding result. We also discuss various extensions to our embeddings

Nightside condensation of iron in an ultra-hot giant exoplanet

Ultra-hot giant exoplanets receive thousands of times Earth's insolation. Their high-temperature atmospheres (>2,000 K) are ideal laboratories for studying extreme planetary climates and chemistry. Daysides are predicted to be cloud-free, dominated by atomic species and substantially hotter than nightsides. Atoms are expected to recombine into molecules over the nightside, resulting in different day-night chemistry. While metallic elements and a large temperature contrast have been observed, no chemical gradient has been measured across the surface of such an exoplanet. Different atmospheric chemistry between the day-to-night ("evening") and night-to-day ("morning") terminators could, however, be revealed as an asymmetric absorption signature during transit. Here, we report the detection of an asymmetric atmospheric signature in the ultra-hot exoplanet WASP-76b. We spectrally and temporally resolve this signature thanks to the combination of high-dispersion spectroscopy with a large photon-collecting area. The absorption signal, attributed to neutral iron, is blueshifted by -11+/-0.7 km s-1 on the trailing limb, which can be explained by a combination of planetary rotation and wind blowing from the hot dayside. In contrast, no signal arises from the nightside close to the morning terminator, showing that atomic iron is not absorbing starlight there. Iron must thus condense during its journey across the nightside.Comment: Published in Nature (Accepted on 24 January 2020.) 33 pages, 11 figures, 3 table

On the Expressiveness of Multiparty Sessions

This paper explores expressiveness of asynchronous multiparty sessions. We model the behaviours of endpoint implementations in several ways: (i) by the existence of different buffers and queues used to store messages exchanged asynchronously, (ii) by the ability for an endpoint to lightly reconfigure his behaviour at runtime (flexibility), (iii) by the presence of explicit parallelism or interruptions (exceptional actions) in endpoint behaviour. For a given protocol we define several denotations, based on traces of events, corresponding to the different implementations and compare them

Police’s competition

Par concours de police, il faut entendre articulation des rapports entre les différentes polices qui peuvent exister en France. Ainsi, l’objet de mes recherches se subdivise-t-il en deux parties. La première porte sur l’étude des concours fonctionnels de police alors que la seconde est consacrée aux concours organiques. L’analyse des concours fonctionnels de police examine les différentes façons de régler une éventuelle concurrence entre plusieurs polices administratives – générales et/ou spéciales. Cette approche entraine ainsi nécessairement un examen des autorités de police administrative chargées de prendre de telles mesures de police. Ce travail nous a permis de constater une grande prise en compte des hypothèses de concours par la jurisprudence avec, néanmoins, parfois, des incertitudes résultant, notamment, de l’évolution de la société et du vieillissement de certaines décisions pourtant toujours en vigueur. Les concours organiques nécessitent, quant à eux, que l’on se livre à un exposé sur l’articulation des rapports entre les différentes forces de police françaises – tant locales ou que nationales. En d’autres termes, cela implique de prendre en compte la police et la gendarmerie nationales ainsi que les polices municipales et intercommunales. Il nous a ainsi semblé opportun d’envisager les différentes possibilités données au législateur et à la jurisprudence pour tenter de prévenir tout risque de concours. L’objectif étant, in fine, d’assurer le plus efficacement possible la sécurité publique sur l’ensemble du territoire national.The subject handles competitions of police on a functional and material drawing. Our work aims at studying the competitive relationships between the various measures of administrative polices – dress and special – and between the national police forces – police nationale and gendarmerie nationale – and local forces

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Les concours de police

The subject handles competitions of police on a functional and material drawing. Our work aims at studying the competitive relationships between the various measures of administrative polices – dress and special – and between the national police forces – police nationale and gendarmerie nationale – and local forces.Par concours de police, il faut entendre articulation des rapports entre les différentes polices qui peuvent exister en France. Ainsi, l’objet de mes recherches se subdivise-t-il en deux parties. La première porte sur l’étude des concours fonctionnels de police alors que la seconde est consacrée aux concours organiques. L’analyse des concours fonctionnels de police examine les différentes façons de régler une éventuelle concurrence entre plusieurs polices administratives – générales et/ou spéciales. Cette approche entraine ainsi nécessairement un examen des autorités de police administrative chargées de prendre de telles mesures de police. Ce travail nous a permis de constater une grande prise en compte des hypothèses de concours par la jurisprudence avec, néanmoins, parfois, des incertitudes résultant, notamment, de l’évolution de la société et du vieillissement de certaines décisions pourtant toujours en vigueur. Les concours organiques nécessitent, quant à eux, que l’on se livre à un exposé sur l’articulation des rapports entre les différentes forces de police françaises – tant locales ou que nationales. En d’autres termes, cela implique de prendre en compte la police et la gendarmerie nationales ainsi que les polices municipales et intercommunales. Il nous a ainsi semblé opportun d’envisager les différentes possibilités données au législateur et à la jurisprudence pour tenter de prévenir tout risque de concours. L’objectif étant, in fine, d’assurer le plus efficacement possible la sécurité publique sur l’ensemble du territoire nationa