A Theory of Regret and Information

Following Quiguin (1994), we propose a general model of preferences that accounts for individuals\' regret concerns. By confronting the commonly-accepted additive and multiplicative regret utility functions to this model, we establish certain characteristics that these utility functions require to be in conformity with our preferences model. Equally, as regret is intrinsically related to the concept of information about the foregone alternatives, we generalize our framework so that it can accomodate any information structure. We show that the less informative that structure is, the higher the utility of a regretful individual. This result means that an individual prefers not to be exposed to ex post information about the foregone alternatives. We also focus on information value, and consider two cases. That of flexibility, where information arrives before the choice and can be used to determine the optimal strategy; that of non-flexibility, where information arrives after the choice. We show that information value is negative when there is no flexibility, and that it can also be negative when there is flexibility., information, choice under uncertainty, bivariate risk aversion

A simple parameter-free and adaptive approach to optimization under a minimal local smoothness assumption

We study the problem of optimizing a function under a \emph{budgeted number of evaluations}. We only assume that the function is \emph{locally} smooth around one of its global optima. The difficulty of optimization is measured in terms of 1) the amount of \emph{noise} $b$ of the function evaluation and 2) the local smoothness, $d$, of the function. A smaller $d$ results in smaller optimization error. We come with a new, simple, and parameter-free approach. First, for all values of $b$ and $d$, this approach recovers at least the state-of-the-art regret guarantees. Second, our approach additionally obtains these results while being \textit{agnostic} to the values of both $b$ and $d$. This leads to the first algorithm that naturally adapts to an \textit{unknown} range of noise $b$ and leads to significant improvements in a moderate and low-noise regime. Third, our approach also obtains a remarkable improvement over the state-of-the-art SOO algorithm when the noise is very low which includes the case of optimization under deterministic feedback ($b=0$). There, under our minimal local smoothness assumption, this improvement is of exponential magnitude and holds for a class of functions that covers the vast majority of functions that practitioners optimize ($d=0$). We show that our algorithmic improvement is borne out in experiments as we empirically show faster convergence on common benchmarks

An authorization model for XML databases

Université de Pau et des Pays de l’Adou

Logical Foundations of Multilevel Databases

International audienceIn this paper, we propose a formal model for multilevel databases. This model aims at being a generic model, that is it can be interpreted for any kind of database (relational, object-oriented...). Our model has three layers. The first layer corresponds to a model for a non-protected database. The second layer corresponds to a model for a multilevel database. In this second layer, we propose a list of theorems that must be respected in order to build a secure multilevel database. We also propose a new solution to manage cover stories without using the ambiguous technique of polyinstantiation. The third layer corresponds to a model for a MultiView database, that is, a database that provides at each security level a consistent view of the multilevel database. Finally, as an illustration, we interpret our 3-layer model in the case of an object-oriented database

Cover Story Management

International audienceIn a multilevel database, cover stories are usually managed using the ambiguous technique of polyinstantiation. In this paper, we define a new technique to manage cover stories and propose a formal representation of a multilevel database containing cover stories. Our model aims to be a generic model, that is, it can be interpreted for any kind of database (e.g. relational, object- oriented etc). We then consider the problem of updating a multilevel database containing cover stories managed with our technique

PLACID: un planificateur pour composer dynamiquement des Services IHM

National audienceDynamic Services Composition (DSC) aims at composing interactive \ systems from a set of available services corresponding \ to the available components. A component consists of a \ Functional Core and/or of a User Interface (UI) respectively \ providing computation and/or representation functions. In \ software engineering, a part of the literature focuses on the \ dynamic composition of computation services. Making the \ hypothesis that UI services can also be composed leads to a \ new research area in Human Computer Interaction: the dynamic \ composition of UI services. This paper presents a planning algorithm that aims to solve the DSC problem. This algorithm produce the task model of the composed UI allowing the user to achieve his/her goal.La Composition Dynamique de Services a pour but de composer un système interactif à partir d’un ensemble de services disponibles correspondant à des composants.Un composant est constitué d’une partie fonctionnelle et d’une partie Interface Homme-Machine (IHM). En Génie Logiciel, la grande majorité de la littérature se concentre sur la composition dynamique de services fonctionnels.Si l’on fait l’hypothèse qu’un service IHM peut aussi être composé, cela entraine une nouvelle problématique de recherche en Interaction Homme-Machine : la Composition Dynamique de Services IHM. Cet article présente un algorithme de planification permettant de résoudre le problème de la composition dynamique d’IHM pour produire le modèle de tâches de l’IHM composée permettant à l’utilisateur d’atteindre son objectif

Optimal regulation of a fully insured deposit banking system

We analyze risk sensitive incentive compatible deposit insurance in the presence of private information when the market value of deposit insurance can be determined using Merton's (1997) formula. We show that, under the assumption that transferring funds from taxpayers to financial institutions has a social cost, the optimal regulation combines different levels of capital requirements combined with decreasing premia on deposit insurance. On the other hand, it is never efficient to require the banks to hold riskless assets, so that narrow banking is not efficient. Finally, chartering banks is necessary in order to decrease the cost of asymmetric information.Regulation,mechanism design,deposit insurance pricing,capital requirements