Interaction and communication among autonomous agents in multiagent systems

The main goal of this doctoral thesis is to investigate a fundamental topic of research within the Multiagent Systems paradigm: the problem of defining open, heterogeneous, and dynamic interaction frameworks. That is to realize interaction systems where multiple agents can enter and leave dynamically and where no assumptions are made on the internal structure of the interacting agents. Such topic of research has received much attention in the past few years. In particular the need to realize applications where artificial agents can interact negotiate, exchange information, resources, and services has become more and more important thanks to the advent of Internet. I started my studies by developing a trading agent that took part to an international trading on-line game: the First Trading Agent Competition (TAC). During the design and development phase of the trading agent some crucial and critical troubles emerged: the problem of accurately understanding the rules that govern the different auctions; and the problem of understanding the meaning of the numerous messages. Another general problem is that the internal structure of the developed trading agent have been strongly determined by the peculiar interface of the interaction system, consequently without any changes in its code, it would not be able to take part to any other competition on the Web. Furthermore the trading agent would not have been able to exploit opportunities, to handle unexpected situations, or to reason about the rules of the various auctions, since it is not able to understand the meaning o the exchanged messages. The presence of all those problems bears out the need to find a standard common accepted way to define open interaction systems. The most important component of every interaction framework, as is remarked also by philosophical studies on human communication is the institution of language. Therefore I start to investigate the problem of defining a standard and common accepted semantics for Agent Communication Languages (ACL). The solutions proposed so far are at best partial, and are considered as unsatisfactory by a large number of specialists. In particular, they are unable to support verifiable compliance to standards and to make agents responsible for their communicative actions. Furthermore such proposals make the strong assumption that every interacting agent may be modeled as a Belief-Desire-Intention agent. What is required is an approach focused on externally observable events as opposed to the unobservable internal states of agents. Following Speech Act Theory that views language use as a form of action, I propose an operational specification for the definition of a standard ACL based on the notion of social commitment. In such a proposal the meaning of basic communicative acts is defined as the effect that it has on the social relationship between the sender and the receiver described through operation on an unambiguous, objective, and public "object": the commitment. The adoption of the notion of commitment is crucial to stabilize the interaction among agents, to create an expectation on other agents behavior, to enable agents to reason about their and other agents actions. The proposed ACL is verifiable, that is, it is possible to determine if an agent is behaving in accordance to its communicative actions; the semantics is objective, independent of the agent's internal structure, flexible and extensible, simple, yet enough expressive. A complete operational specification of an interaction framework using the proposed commitment-based ACL is presented. In particular some sample applications of how to use the proposed framework to formalize interaction protocols are reported. A list of soundness conditions to test if a protocol is sound is proposed

Le brouillon collaboratif: analyse de productions d’élèvesde 5ème HarmoS

Ce travail cherche à intégrer le dispositif du brouillon collaboratif dans une séquence de production écrite de langue 1 dans trois classes de 5ème HarmoS dans le canton de Fribourg en début d’année scolaire. La majeure partie de ce travail réside dans l’analyse quantitative des nombreuses productions textuelles d’élèves ayant participé à notre séquence inédite. Créée spécialement en fonction des planifications des enseignantes, celle-ci traite aussi bien du texte d’itinéraire que du texte transmettant des savoirs à travers des expériences. Notre travail montre que le dispositif du brouillon collaboratif couplé à la révision collaborative permet aux élèves de produire des textes variés et correspondant aux genres textuels abordés, leur apportant donc une aide effective. Il s’agit donc d’un outil didactique qui prend tout son sens dans l’enseignement du français au cycle 2 et qui mérite d’être d’avantage mis en pratique

Learning with summaries: Effects of representation mode and type of learning activity on comprehension and transfer

The purpose of the experiment was to examine whether students better understand a science text when they are asked to self-generate summaries or to study predefined summaries. Furthermore, we tested the effects of verbal and pictorial summaries. The experiment followed a 2 × 2 design with representation mode (verbal vs. pictorial) and learning activity (self-generating vs. studying) as experimental factors. The main dependent variables were learning performance, measured by a comprehension and a transfer test, and strategy use, measured by self-report scales. Seventy-one students (Grade 10) participated in the study. The results showed that studying predefined summaries in a pictorial representation mode facilitated deep understanding. Furthermore, mediation analysis showed that the effect of representational mode was mediated by students' spatial representations of learning content. The effect of spatial representations was in turn facilitated by mental imagery activities

Involvement of nucleus accumbens dopamine D1 receptors in ethanol drinking, ethanol-induced conditioned place preference, and ethanol-induced psychomotor sensitization in mice

Rationale: Dopamine D1 receptor (D1R) signaling has been associated to ethanol consumption and reward in laboratory animals.Objectives: Here, we hypothesize that this receptor, which is located within the nucleus accumbens (NAc) neurons, modulates alcohol reward mechanisms.Methods: To test this hypothesis, we measured alcohol consumption and ethanol-induced psychomotor sensitization and conditioned place preference (CPP) in mice that received bilateral microinjections of small interference RNA (siRNA)-expressing lentiviral vectors (LV-siD1R) producing D1R knock-down. The other group received control (LV-Mock) viral vectors into the NAc.Results: There were no differences in the total fluid consumed and also no differences in the amount of ethanol consumed between groups prior to surgery. However, after surgery, the LV-siD1R group consumed less ethanol than the control group. This difference was not associated to taste neophobia. In addition, results have shown that down-regulation of endogenous D1R using viral-mediated siRNA in the NAc significantly decreased ethanol-induced behavioral sensitization as well as acquisition, but not expression, of ethanol-induced place preference.Conclusions: We conclude that decreased D1R expression into the NAc led to reduced ethanol rewarding properties, thereby leading to lower voluntary ethanol consumption. Together, these findings demonstrate that the D1 receptor pathway within the NAc controls ethanol reward and intake