Semantic subtyping for objects and classes

In this paper we propose an integration of structural subtyping with boolean connectives and semantic subtyping to define a Java-like programming language that exploits the benefits of both techniques. Semantic subtyping is an approach for defining subtyping relation based on set-theoretic models, rather than syntactic rules. On the one hand, this approach involves some non trivial mathematical machinery in the background. On the other hand, final users of the language need not know this machinery and the resulting subtyping relation is very powerful and intuitive. While semantic subtyping is naturally linked to the structural one, we show how our framework can also accommodate the nominal subtyping. Several examples show the expressivity and the practical advantages of our proposal

The Powerdomain of Indexed Valuations

This paper is about combining nondeterminism and probabilities. We study this phenomenon from a domain theoretic point of view. In domain theory, nondeterminism is modeled using the notion of powerdomain, while probability is modeled using the powerdomain of valuations. Those two functors do not combine well, as they are. We define the notion of powerdomain of indexed valuations, which can be combined nicely with the usual nondeterministic powerdomain. We show an equational characterization of our construction. Finally we discuss the computational meaning of indexed valuations, and we show how they can be used, by giving a denotational semantics of a simple imperative language

Mobilités et reconfiguration des territorialités collectives en montagne : l'engagement des acteurs mobiles dans les processus de patrimonialisation au Maroc

International audienceThis study analyzes the role of mobility in processes of territorialisation. It focuses on projects promoting Jewish heritage now under way in the mountains of Morocco and is interested in the engagement of mobile actors, particularly from the Moroccan Jewish diaspora, in advancing these initiatives. Drawing on the field of post-national studies, and applying a qualitative methodological approach, it shows that these actors, during their life course, have made major displacements, including rural to urban migration and international emigration, during which they have accrued contacts, resources and knowledge that now prove useful in advancing heritage projects in their regions of origin in Morocco. The projects of the Jewish diaspora can conflict with those advanced by other local actors or with the visions of the local inhabitants. The study examines the conflicts that arise; the identifications, memories, and distinct territorialities that are bring into play; and the manner with which these are negotiated - giving birth to hybrid territorialities.La recherche présentée ici a pour objectif d’analyser le rôle joué par les mobilités dans les processus de territorialisation. Elle porte sur des projets de valorisation du patrimoine juif en cours de réalisation dans les montagnes marocaines et s’intéresse à l’engagement d’acteurs mobiles, notamment de la diaspora juive, dans ces projets. En appui sur le champ des études post-nationales et dans le cadre d’une démarche méthodologique qualitative, elle montre comment ces acteurs font des déplacements qui jalonnent leurs parcours individuels des ressources qu’ils mettent au service de leurs projets. Les projets de la diaspora juive seront confrontés à ceux portés par les autres acteurs locaux et à la perception qu’en ont les habitants. Il s’agira d’examiner les conflits qui surgissent, les identifications, les mémoires, les territorialités différentes qu’ils mettent en jeu et la manière avec laquelle elles sont négociées, donnant naissance à des territorialités hybrides

Processes, Systems \& Tests: Defining Contextual Equivalences

In this position paper, we would like to offer and defend a new template to study equivalences between programs -- in the particular framework of process algebras for concurrent computation.We believe that our layered model of development will clarify the distinction that is too often left implicit between the tasks and duties of the programmer and of the tester. It will also enlighten pre-existing issues that have been running across process algebras as diverse as the calculus of communicating systems, the $\pi$-calculus -- also in its distributed version -- or mobile ambients.Our distinction starts by subdividing the notion of process itself in three conceptually separated entities, that we call \emph{Processes}, \emph{Systems} and \emph{Tests}.While the role of what can be observed and the subtleties in the definitions of congruences have been intensively studied, the fact that \emph{not every process can be tested}, and that \emph{the tester should have access to a different set of tools than the programmer} is curiously left out, or at least not often formally discussed.We argue that this blind spot comes from the under-specification of contexts -- environments in which comparisons takes place -- that play multiple distinct roles but supposedly always \enquote{stay the same}.We illustrate our statement with a simple Java example, the \enquote{usual} concurrent languages, but also back it up with $\lambda$-calculus and existing implementations of concurrent languages as well

Typed event structures and the p-calculus

We propose a typing system for the true concurrent model of event structures that guarantees an interesting behavioural property known as confusion freeness. A system is confusion free if nondeterministic choices are localised and do not depend on the scheduling of independent components. It is a generalisation of con uence to systems that allow nondeterminism. Ours is the rst typing system to control behaviour in a true concurrent model. To demonstrate its applicability, we show that typed event structures give a semantics of linearly typed version of the p-calculi with internal mobility. The semantics we provide is the rst event structure semantics of the p-calculus and generalises Winskel's original event structure semantics of CCS

ORGANIZATIONAL AND TRADE ISSUES IN THE SUPPLY CHAIN OF MAIZE AND SOYBEAN: THE ROLE OF GM AND NON-GM PRODUCTS

Da oltre vent’anni l’Unione Europea (UE) è protagonista di un acceso dibattito circa l’orami vasta adozione di OGM in agricoltura. Laddove la maggior parte dei paesi Nord e Sud americani ha già largamente introdotto tali colture, l’UE è invece in forte ritardo, complice una legislazione basata sul Principio di Precauzione. Queste discrepanze nei i processi legislativi hanno portato a galla alcune problematiche di carattere commerciale: primo, la riduzione delle disponibilità di materia prima non-OGM costituisce un problema per la stabilità delle filiere ad essa dedicate; secondo, il commercio di prodotti convenzionali è compromesso dalla possibilità di riscontrare varietà OGM non approvate in UE all’interno delle partite provenienti da paesi terzi. In ultimo, data l’ampia diffusione di OGM nelle Americhe, è lecito porsi il quesito di come tale tendenza abbia influito sui prezzi delle materie prime agricole. In questa tesi si cercherà di analizzare queste tematiche. Per prima cosa, ci occupiamo di capire come la filiera della soia non-OGM italiana sia organizzata e gestita in modo da minimizzare i rischi di presenza avventizia. La conclusione è che le forme di governance ibride garantiscono la migliore forma di gestione. Successivamente ci domandiamo se le diversità legislative in materia di OGM abbiamo un impatto sull’import Europeo di mais e soia. Utilizzando l’analisi della domanda, riscontriamo che i paesi esportatori competono o sul prezzo o in base alla disponibilità stagionale di prodotto. In ultimo, utilizzando serie storiche, analizziamo il ruolo del tasso di adozione di soia OGM sui prezzi reali; ciò che osserviamo indica che questo ha un effetto deflattivo di breve periodo, ma di scarso peso.The debate on the increasing adoption of GMOs in agriculture has been in vogue for the last twenty years. Whereas most North and South American countries have largely adopted GMOs, the European Union (EU) has not. Since the EU legislation is based on the Precautionary Principle, the introduction of new GM varieties has been slow. These discrepancies put forward some fundamental issues: first, the decreasing availability of non-GM raw materials poses the sustainability of these supply chains at risk; second, the trade of conventional products is undermined by the possible occurrence of unauthorized GMOs in overseas. Last, the wide adoption of GM crops in North and Latin America poses the question of what effect the spreading of biotechnology in agriculture has exerted on market prices. In this thesis, we try to answer these three research questions. First of all, we investigate how the Italian supply chain for non-GM soybean meal is framed and managed in order to reduce the risk of adventitious presence. We find that hybrid organizations represent the best governance form. Next, we assess the role of legislative diversities (regarding GMOs) on EU import decisions through import demand analysis. We conclude that competition among exporters is solely based on price and seasonality. Last, we disentangle the role of GMOs adoption on the variability of US soybean prices. Results indicate that a higher rate of adoption reduces real soybean market prices, yet the effect is short lived and not much relevant

A compositional semantics for the reversible pi-calculus

International audienceWe introduce a labelled transition semantics for the reversible pi-calculus. It is the first account of a com- positional definition of a reversible calculus, that has both concurrency primitives and name mobility. The notion of reversibility is strictly linked to the notion of causality. We discuss the notion of causality induced by our calculus, and we compare it with the existing notions in the literature, in particular for what concerns the syntactic feature of scope extrusion, typical of the pi-calculus

Ressources territoriales et destinations touristiques : des couples en devenir ?: Les expériences de production du safran à Taliouine (Maroc) et de l'oignon dans l'Aïr (Niger)

L'article est en cours d'édition dans la Revue de Géographie Alpinecultural tourism rests on the construction of destinations carrying recognized and sought outside qualities. It is a set of specific resources whose singularity is justified by an anchoring with the territories which produce them. This article proposes a grid of analysis of the resource, through three stages: the revelation, the development and the articulation with other resources. This grid of analysis is then applied to various situations observed in Morocco and Niger. This approach makes it possible to look further into the concept of quality associated with a resource and to question the conditions of formation of the basket of goods, associating commercial objects and non-commercial objects. This Co-construction leads to the association of objects of which certain qualities could be transposed to other objects, because of their anchoring with the territory.Le tourisme culturel repose sur la construction de destinations porteuses de qualités reconnues et recherchées à l'extérieur. C'est un ensemble de ressources spécifiques dont la singularité est justifiée par un ancrage aux territoires qui les produisent. Le présent article propose une grille d'analyse de la ressource, en approfondissant la phase de révélation. Cette grille est ensuite appliquée à différentes situations observées au Maroc et au Niger. Cette approche permet d'approfondir la notion de qualité associée à une ressource et d'interroger les conditions de formation du panier de biens, associant des objets marchands et des objets non marchands. Cette co-construction aboutit à l'association d'objets dont certaines qualités vont pouvoir être transposées à d'autres objets, du fait de leur ancrage au territoire