A Formalization of Polytime Functions

We present a deep embedding of Bellantoni and Cook's syntactic characterization of polytime functions. We prove formally that it is correct and complete with respect to the original characterization by Cobham that required a bound to be proved manually. Compared to the paper proof by Bellantoni and Cook, we have been careful in making our proof fully contructive so that we obtain more precise bounding polynomials and more efficient translations between the two characterizations. Another difference is that we consider functions on bitstrings instead of functions on positive integers. This latter change is motivated by the application of our formalization in the context of formal security proofs in cryptography. Based on our core formalization, we have started developing a library of polytime functions that can be reused to build more complex ones.Comment: 13 page

Certification of Origin and Brands Competition

We analyse the competition in quality and quantity between a foreign firm and a domestic firm. The domestic firm can belong to a certification of origin, whereas its rival uses a pure brand strategy. We will show how the certification can allow the domestic firm to position itself as a high quality producer and improve the average quality of the products offered on the market. If, however, the certified firm offers the low quality good, the certification can permit it to guarantee a higher profit than that of its competitor and to improve the consumers' surplus by favouring product standardisation.Certification of origin, Quality, international competition, Demand and Price Analysis, L13, F12, F14,

Universities and knowledge intensive business services as actors of the creative regional technological infrastructure: The case of the Upper-Rhine Valley

Characterizing the innovative capacity of a territory, and his specific attractivity for external direct investment in new fields, needs the definition of measurable concepts and the design of a proper methodology to gather relevant quantitative data. The aim of the paper is to propose a general theoretical view of the functional characteristics of the various actors and institutions that compose the ?technological infrastructure? of a region, then to show some results of studies made in the Upper-Rhine Valley (in France as well as in Germany) that cast a light on the contribution of certain important players like universities and ?knowledge intensive business services?. Universities have an important and very composite economic impact in their region. As a regular public administration they contribute to local economic activity throug personal incomes, capital expenses and current expenses. But they also attract students, contribute to the image of the city and sometimes propose valuable services for firms. Where universities (and public research centers associated to them) play a very specific role is by training young researchers, who are at the same time inputs and outputs of the research process and fulfill an important role in the cooperation and transfer networks with the most creative local firms. New types of knowledge intensive services are increasingly developed in the environment of industrial firms, either as a result of the process or of ?externalization? of large firms or as an autonomous process of creation ? for instance start-ups initiated by the academic system, but other sorts of services too. These business services could play a crucial role not only for large technology based firms, but also for the small firms at the basis of the regional industrial fabrique. They participate to the technological infrastructure, and more largely to the managerial skills? supply and the innovative climate of the territory.

Agrifood safety standards, market power and consumer misperceptions

This paper analyzes how the implementation of a food safety standard affects firms strategic behaviour within the context of a food chain. We provide a formal analysis, which considers that the sanitary risk results from a strong heterogeneity of upstream production conditions and the final demand depends on consumers risk estimations (given that consumers may underestimate or, conversely, overestimate the sanitary risk). We show how downstream (processing or retailing) firms may be prompted to play a positive role with respect to food safety, either by selecting only the safest upstream producers or by encouraging the improvement of suppliers production conditions. When the degree of consumers risk misperception is relatively low, then a downstream firm may adopt the latter strategy and increase the marketed quantities as the food safety standard is improved. However, we show that the actual contamination risk is not necessarily decreasing in the level of the food safety standard.food safety standards, market power, risk misperception, Food Consumption/Nutrition/Food Safety,

Minimum Quality Standards and brand development in agrifood chains

This paper develops an original framework to better understand the interaction between the development of brands and the quality of raw materials. We consider different levels of consumer trust for a brand and we examine the incentive for firms to improve the quality of a processed product by requiring that upstream suppliers adopt a private standard. In contrast to previous literature, the incentive for firms to develop a more stringent private standard may increase with the level of the regulated minimum quality standard. Moreover, the creation of a private standard can reduce the risk of consumer dissatisfaction while increasing the marketed quantity. Unexpected positive effects of a reinforcement of the minimum quality standard may arise, in the sense that both market access for upstream producers and consumer surplus are improved and final price may decrease with respect to simply complying with the regulation.Minimum Quality Standard, brand, vertical relationship, Agribusiness,

Retailer-led Regulation of Food Safety : Back to Spot Markets?

At the end of the 1990s European retailers had significantly contributed to restructuring fresh agricultural product food chains (meat, fruit and vegetables), and had turned away from spot markets in order to create their own supply chains, based on private technical requirements and verification systems usually managed from within the firm. However, over the last few years a second type of system has appeared, as the range of standards adopted by retailers has been broadened to include generic standards common to several retailers. A telling example of this new approach is provided by the EUREPGAP protocol. In this paper we propose a theoretical analysis of this new procedure and its possible impacts.food safety, spot markets, retailer, supply chain, Food Consumption/Nutrition/Food Safety,

Temps du passé et temps passé : le présent refiguré dans quelques récits de science-fiction

Le thème classique du retour dans le passé en science-fiction n'en apprend-il pas plus sur les caractères du présent que sur le passé proprement dit ? L'exploration fictive du passé amène souvent à majorer la figure du passé (l'insistance sur les paradoxes temporels dans le cas du voyage temporel en est l'exemple) au détriment de la figure du présent, souvent minorée, car le passé, considéré comme intangible, semble se suffire et être par conséquent indépendant du présent. Il faut renverser cette perspective : l'exploration du passé modifie la perspective du présent. L'analyse des Temps parallèles de R. Silverberg , comparée à celle de deux œuvres offrant des approches différentes, pourra contribuer à revaloriser la dimension du présent

Personalisation in social work - A comparative study of the professional socialisation of social work students in a university and technical college training course

The processes of professionalisation and professional socialisation are examined both generally and in the context of an occupation undergoing professionalisation - namely social work. The way in which commitment to a profession develops amongst students in training, including changes in the conceptions which students have of the profession and situations which are important in bringing about change, is examined. There is a comparison of students in different educational institutions, a University and a Technical College, and with different educational backgrounds. The goals and structure of the institutions, including their teaching staff, are also discussed. The value of a number of models or typologies of professional socialisation, in particular the process model, in suggesting approaches to the research and in distinguishing levels of analysis, are considered. A questionnaire survey was carried out in two training courses and students were interviewed at the beginning and end of their courses. Amongst other things material was collected on the social characteristics and background of students, motivations for entry to social work, experiences on the course and aspects of identification with the profession. Information was also obtained from documentary sources and informal interviews with staff on the organisation and control of training, the curriculum and college courses, selection procedures and the characteristics of teaching staff. On the basis of this data it was possible to identify and distinguish between certain structural variables (such as student selection) and situations in which socialisation took place (such as role playing) and to suggest which variables were of greatest importance in socialisation. The information also threw some light on the relative strengths and weaknesses of the various models and typologies under discussion and suggested how these might be developed and improved. Finally the data from the research is used in a discussion of some of the contemporary problems in social work training and education.<p

" Jeux de langage " et épistémologie de l'argumentation à l'école primaire : du têtard à la grenouille.

This paper is an analysis of argumentative dialogues relating to the teaching of the biological sciences based on the theoretical model of "language game" in the context of semantic logic developed during the twentieth century (Frege, Quine). The model of "language game" is mobilized to define the coexistence of a plurality of references for ordinary-language words. We show how this polysemy can serve as the basis for an interrogation that can permit an argument-based dialogue to pose conceptual foundations for a given domain of knowledge. The epistemological interest of the argumentation results from the play of oppositions linked to the semantic variation of the linguistic terms. Our contribution emphasizes the didactic and epistemological role played by the posing of questions in the classroom. The claims are illustrated using the transcripts of discussions in the second cycle of primary school concerning the transformation of tadpoles into frogs.La contribution analyse le dialogue argumentatif à propos d'un enseignement de sciences biologiques à l'aide du modèle théorique des " jeux de langage " qui s'est développé au cours du siècle dernier dans le courant de la sémantique logique (Frege, Quine). Le modèle du " jeu de langage " est défini comme la coexistence dans les mots du langage d'une pluralité référentielle qui est à la source d'un questionnement permettant au dialogue argumentatif de construire les bases conceptuelles du savoir en jeu. L'enjeu épistémologique de l'argumentation résulte du travail d'opposition lié à la variation sémantique des termes du langage. La contribution insiste sur le rôle didactique et épistémologique du questionnement dans la classe. Ces thèses sont illustrées par l'analyse de la transcription d'une séquence au cycle deux de l'école primaire, sur le thème de la transformation du têtard en grenouille

De la science fiction à la fiction en sciences : Abbott, ou l'enseignement de la géométrie

International audienceLe roman de science-fiction "Flatland" (Abott) montre comment une fiction littéraire peut engendrer un questionnement épistémologique sur l'espace géométrique de mondes parallèles entre eux. Il aborde une question didactique : est-il possible pour un sujet de construire une géométrie à trois dimensions en partant d'un monde à deux dimensions