Artificial institutions: a model of institutional reality for open multiagent systems

Software agents' ability to interact within different open systems, designed by different groups, presupposes an agreement on an unambiguous definition of a set of concepts, used to describe the context of the interaction and the communication language the agents can use. Agents' interactions ought to allow for reliable expectations on the possible evolution of the system; however, in open systems interacting agents may not conform to predefined specifications. A possible solution is to define interaction environments including a normative component, with suitable rules to regulate the behaviour of agents. To tackle this problem we propose an application-independent metamodel of artificial institutions that can be used to define open multiagent systems. In our view an artificial institution is made up by an ontology that models the social context of the interaction, a set of authorizations to act on the institutional context, a set of linguistic conventions for the performance of institutional actions and a system of norms that are necessary to constrain the agents' action

Artificial institutions: a model of institutional reality for open multiagent systems

Software agents’ ability to interact within different open systems, designed by different groups, presupposes an agreement on an unambiguous definition of a set of concepts, used to describe the context of the interaction and the communication language the agents can use. Agents’ interactions ought to allow for reliable expectations on the possible evolution of the system; however, in open systems interacting agents may not conform to predefined specifications. A possible solution is to define interaction environments including a normative component, with suitable rules to regulate the behaviour of agents. To tackle this problem, we propose an application-independent model of artificial institutions that can be used to define open multiagent systems. With respect to other approaches to artificial (or electronic) institutions, which mainly focus on the definition of the normative component of open systems, our proposal has a wider scope, in that we model the social context of the interaction, define the semantics of an Agent Communication Language to operate on such a context, and give an operational definition of the norms that are necessary to constrain the agents’ actions. In particular, we define the semantics of a library of communicative acts in terms of operations on agents’ social reality, more specifically on commitments, and regard norms as event-driven rules that, when fired by events happening in the system, create or modify a set of commitments. An interesting aspect of our proposal is that both the definition of the ACL and the definition of norms are based on the same notion of commitment. Therefore an agent capable of reasoning on commitments can reason both on the semantics of communicative acts and on the normative system

Molecular simulations as test beds for bridging high throughput and high performance computing

La forte connotation de la chimie computationnelle en termes de technologies informatiques est en même temps la force et la faiblesse des simulations moléculaires. En effet, dans le but de réaliser des études de ce type(même pour les systèmes contenant un petit nombre d'atomes), il faut d'abord procéder à des calculs de structure électronique de haut niveau. Ces calculs nécessitent généralement des nœuds (ou clusters de nœuds) équipés de mémoires de grande taille (de l'ordre de plusieurs Go), et de processeurs performants au niveau de plusieurs Gigaflops. Celà parce que la surface d'énergie potentielle ensemble (PES) qui régît le mouvement nucléaire doit être élaborée préalablement. Sur des plate-formes High Performance Computing (HPC) avec des capacités parallèles améliorées nous pouvons exécuter simultanément, sur plusieurs single (ou clusters de) processeurs multicœurs, le calculs requis par le grand nombre des valeurs d'énergie potentielles nécessaires pour décrire les PES explorés par une processus de réactivité chimique. Le véritable goulot d'étranglement dans la réalisation des calculs nécessaires, en effet, est représentée par la disponibilité d'une plate-forme informatique ayant des exigences informatiques appropriées en matière de temps de calcul et de mémoire physique. Les capacités de calcul (limitée) en général accessibles à la communauté scientifique, en fait, a toujours fixé des limites sévères à l'élaboration d'un système informatique complet de simulation a priori des processus moléculaires. Heureusement, des technologies informatiques innovantes, alliant la concurrence et la mise en réseau (tels que l'informatique distribuée, les laboratoires virtuels, le calcul intensif, le "Grid computing") ouvrent des perspectives nouvelles à la possibilité de réaliser d'importants débits de calcul et, par conséquent, de développer des simulations moléculaires a priori des systèmes réels. Les fondements théoriques et les paradigmes informatiques utilisés pour l'assemblage des composants du "Grid Empowered Molecular Simulator" (GEMS) sont décrits dans le Chapitre 1. Dans ce chapitre, nous illustrons le développement de workflows basés sur la grille, qui permettent l'évaluation ab initio des propriétés observables des systèmes chimiques petits à partir du calcul des propriétés électroniques. Dans le chapitre 2 nous abordons la question de l'interopérabilité entre codes de calcul à travers les différentes étapes du flux de travail (workflow). Ce chapitre propose les formats Q5cost et D5cost comme modèles "standard de facto" pour les calculs de chimie quantique. Le Chapitre 3 porte sur les résultats de calculs ab initio autonomes effectués sur des différents systèmes chimiques (petits clusters X_4 (X=Li,Na,K,Cu) ainsi que le dimère BeH-). Le chapitre traite des liaisons chimiques particulières et intéressantes présentes dans ces systèmes, qui nécessitent de méthodes quantiques de haut niveau à fin d'une possible rationalisation. Enfin, les chapitre 4 et 5 concernent respectivement les résultats de notre travail sur deux problèmes de combustion et la chimie atmosphérique (l'isomérisation CH3CH2OO• et la réaction N2+N2). Ils visent tous les deux à la construction des PES pour un processus réactif. Une fois la PES générée, les données cinétiques et dynamiques doivent être calculées pour un grand nombre de conditions initiales, et cela peut être fait sur des plateformes HTC. L'assemblage des workflows informatiques pour l'utilisation couplée des systèmes HPC et HTC est également traitée dans cette thèse.The strong connotation of computational chemistry in terms of computer technologies is at the same time the strength and the weakness of molecular simulations. As a matter of fact, in order to perform such studies (even for few-atom systems) we first need to carry out high-level electronic structure calculations. These calculations typically require nodes (or clusters of nodes) equipped with large (of the order of many GB) memories and processors performing at the level of several Gigaflops. This is because the whole Potential Energy Surface (PES) governing the nuclear motion needs to be worked out first. On the High Performance Computing (HPC) platforms with enhanced parallel capabilities we can run concurrently, on several single multicore (or clusters of) processors, the calculations required by the (large number of) potential energy values necessary to describe the PES explored by a reactive chemical process. The real bottleneck in carrying out related computational campaigns, indeed, is represented by the availability of a computing platform having the proper computational requirements in terms of computing time and physical memory. The (limited) computing capabilities in general available to the scientific community, in fact, still set severe limitations to the development of full a priori computational simulations of molecular processes. Fortunately, innovative computing technologies combining concurrency and networking (such as distributed computing, virtual laboratories, supercomputing, Grid computing) are opening new prospects to the possibility of achieving significant computational throughputs and, therefore, of developing a priori molecular simulations of real systems. The theoretical foundations and the computing paradigms employed for the assemblage of the components of the Grid Empowered Molecular Simulator GEMS are described in Chapter 1. In that chapter the development of grid based workflows allowing the ab initio evaluation of the observable properties of small chemical systems starting from the calculation of the electronic properties is illustrated. In Chapter 2 the issue of the of interoperability between computational codes across different stages of the workflow is faced. The Chapter proposes Q5cost and D5cost common data models as de facto standard formats for quantum chemistry calculations. Chapter 3 relates to the results of standalone ab initio calculations performed on different small chemical systems (X4 clusters and BeH- dimer). The Chapter discusses particular and interesting chemical bonds requiring high-level quantum methods to the end of being rationalized. Finally Chapter 4 and Chapter 5 report the results of our work on two combustion and atmospheric chemistry problems (CH3CH2OO• isomerization and N2+N2 reaction) respectively. They both aim at constructing the PES for a reactive process. Once a PES is generated, the kinetic and dynamical data need to be calculated for a large number of initial conditions, and can be computed on HTC platforms. The assemblage of the computational workflows for the coupled use of HPC and HTC systems is also dealt there

A High-Level Ab Initio Study of the N-2 + N-2 Reaction Channel

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Commitments for agent-based supply chain management

As supply chain networks are becoming more and more global, process coordination must be considered a crucial point for successful business management. The need for a suitable management and communication framework is thus becoming evident. We already have some examples showing that information sharing is a key-point at certain levels of a supply chain network. As there are several analogies between a company in a business network and an agent, the Multi-Agent System paradigm can be a valid approach for modelling supply chain networks. We consider commitment as a concept that underlies the whole multi-agent environment, that is, an inter-agent state, reflecting a business relation between two companies that make themselves represented by software agents. We present a data structure for commitments that can be used in the agent-based communication framework for the management of a supply chain. Business partnership between companies leads to the creation of a ”channel ” through which we can identify three different kinds of flow (products, money and information). We show how commitments that deal with these flows are related to one another and how they can affect the supply chain

A Logical Model for Agent Communication Languages

AbstractThe current ACL proposals show some shortcomings with respect to the definition of their semantics. Our paper aims at tackling those issues by defining an ACL semantics as a specification of the analytical effects of agent communicative acts. We analyze agent communication in terms of concepts taken from Speech Act Theory, as several researchers have already done, but move away from the mainstream view of artificial agent research, as we define communicative acts in terms of changes at the level of social relationship between agents. We take commitment to be a primitive concept underlying the social dimension of multiagent systems, and define a basic artificial institution whose aim is to provide agents with the means to affect the commitment network that binds them to each other