{ bourgne,hette,maudet,pinson } @lamsade.dauphine.fr
ABSTRACT
We investigate the properties of a multiagent system where each (distributed) agent locally perceives its environment. Upon perception of an unexpected event, each agent locally computes its favoured hypothesis and tries to propagate it to other agents, by exchanging hypotheses and supporting arguments (observations). However, we further assume that **communication** opportunities are severely constrained and change dynamically. In this paper, we mostly investigate the convergence of such systems towards global consistency. We first show that (for a wide class of protocols that we shall define), the **communication** **constraints** induced by the topology will not prevent the convergence of the system, at the condition that the system dynamics guarantees that no agent will ever be isolated forever, and that agents have un- limited time for computation and arguments exchange. As this assumption cannot be made in most situations though, we then set up an experimental framework aiming at com- paring the relative efficiency and effectiveness of different interaction protocols for hypotheses exchange. We study a critical situation involving a number of agents aiming at es- caping from a burning building. The results reported here provide some insights regarding the design of optimal pro- tocol for hypotheses refinement in this context.

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VI. FIELD RESULTS
The surveillance mission has been experimented with 8 real robots on the field. Two aerial robots and six ground robots with different perception and moving skills were involved. Nine missions were run during an experimental demonstration day on an area of 200m x 200m with scattered buildings. In this section, we present the results obtained for two of these missions. Each mission has 6 **communication** **constraints**, 25 points to observe, 93 robot positions. An initial plan has been computed by HiPOP in approximately 8 seconds for each mission. The initial plans vary by the way observations and communications are allocated to the several robots. However, in all the missions, the initial plan contains 104 actions and lasts around 410 seconds.

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The **communication** **constraints** present in practical MAS networks motivated this research work to investigate and develop distributed control algorithms which must be able to deal with these **constraints** eﬀectively.
• In the second chapter, leader-following consensus problem has been considered. A continuous- discrete time observer has been proposed to estimate the position and the velocity in continuous time through available discrete position data. Each agent not only estimates its own states but also the states of its neighbors. The proposed distributed control law uses these estimated states to compute the required input of the agent. It has been shown through Lyapunov stability analysis that the MAS achieves practical stability with the proposed algorithm if the leader input (acceleration) is nonzero and exponential stability is achieved for the case when the leader is static or moving with some constant velocity. The results have been further expanded for the case when the **communication** topology among the agents does not remain ﬁxed and changes with time. It has been proved that the MAS under the **communication** **constraints** can achieve consensus with switching topologies if the average dwell time remains greater than a certain value. The developed control law has also been validated through MATLAB simulations.

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Despite continual advances in modeling of complex natural processes, ocean fronts at the mesoscale and smaller remain challenging [41,111], and hence have emerged as a primary focus area for mobile sensing systems. Here, progress has been rapid, e.g. [83, 246]. Zhang et al. [261, 262] carried out at-sea experiments where measurements both drove trajectory decisions and triggered collection of large samples. A single vehicle has successfully tracked a plankton bloom [98], while a distributed simulation approach for plume and thermocline tracking is presented in [182]. Supporting all these developments, basic water properties are routinely measured today from mobile robots, while sophisticated chemical and biological analyses in situ are becoming mature technologies, for example DNA probes [216] and mass spectrometers [37]. In turn, ocean modeling is becoming integrated with real-time sampling systems, e.g., [110, 225, 251], and is increasingly taking on multi-disciplinary aspects [230]. Path-planning under knowledge of current forecasts has been studied extensively, for example by Smith et al. [225] and Lolla et al. [149]. None of these works, however, consider cooperation between vehicles, nor **communication** **constraints**. Elsewhere, coordinated sampling using drifters and vehicles has been studied in [61, 105], and collaborative control for tracking Lagrangian coherent structures in [160]. But these papers do not address global dynamic models nor **communication** **constraints**.

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For Figures 4 and 5, the number of processors P used the experiments have been carefully chosen to be written as c(c − 1) so that the rectangular pattern allows all processors to be used. This is not the case for arbitrary values of P and we are faced with the problem of finding a rectangular grid r × c, with (i) r and c close together so that the grid is not too long and the number of different processors per row or column is not too large, and (ii) rc 6 P but close to P so as not to waste resources. In practice, these two **constraints** are not easy to fulfill and their simultaneous implementation naturally leads to choosing a number of processors (a reservation of resources in practice) that is smaller than the number of processors actually available. In this case, the RS strategy proves to be very efficient, because it is agnostic of any property on P and its efficiency does not depend on the value of P .

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These results are proved mathematically and a design methodology is given in the case of NCS composed of interconnected LTI systems.
The use of a **communication** network in NCS considerably reduces the wiring, espe- cially when the control application contains a large number of nodes. Consequently, the maintenance and the deployment become easier. The automotive industry represents an important application field of NCS. The design process of automotive applications is subject to conflicting criteria including cost, safety, reliability and performance. Conse- quently, these networked embedded control applications are developed on target plat- forms with limited CPU speed, memory and **communication** bandwidth. When compu- tation or **communication** resources are limited, they have to be exploited as efficiently as possible. In distributed information processing systems, the scheduling function is re- sponsible for the allocation of computation or **communication** resources. Consequently, using efficiently the computation or **communication** resources amounts to designing ap- propriate scheduling algorithms. Recently, it has been shown that a more efficient use of the computation or **communication** resources could be obtained if the problems of control and resource allocations are considered jointly [Årzén et al., 2000, Cervin et al., 2002, Martí et al., 2004, Lee et al., 2005].

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For the case in which the objective is to maximize the number of regular nodes that achieve throughput at least Tmin, both an exact MILP-based technique and the f[r]

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C. Comparison of Different Network Handling Protocols The scenario used to test the different task adjustment approaches described above involved a team of 12 heteroge- neous agents (6 UAVs and 6 ground robots). The simulation was initialized with 12 UAV tasks with random start times, 40 sec time windows and 5 sec durations. Once the UAV tasks were started a secondary ground robot rescue task was created for each UAV task. Additional pop-up UAV tasks were created at 5 sec intervals and the task allocation algorithm replanned every 2 sec. The simulation consisted of a mission control center, a network detector and local agent simulations. The network detector used the vehicle positions and a **communication** radius parameter to determine if two vehicles were able to communicate and returned a list of subnetworks. The local agent simulations implemented models of the vehicles to execute the tasks in each agent’s path. The mission control center maintained the list of tasks by creating pop-up tasks and pruning completed tasks from the list, in addition to implementing the responsibilities for the different task adjustment methods described in the previous section. The overall mission score was obtained by adding the individual scores for the agents as described in Section II-D

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take into account additional **constraints** arising from the capacities of individual nodes, such as their ability to use only certain frequencies.
Last but not least, a major challenge for future work consists in solving the F3C problem in general graphs using a parallel rather than sequential deterministic algorithm. The new difficulty is then to take into account cycles in a distributed setting in which the global graph topology is not known beforehand, but must be discovered on the fly while avoiding conflicts and collisions.

Les frontières de l 'humain et de la machine posent d’autres questions. Les analyses de la **communication** rejoignent deux grandes traditions de confrontation entre l’humain et la machine. En premier lieu, un questionnement sur l’individu humain et l’objet machine. La machine n'a pas ce qui nous est le plus caractéristique : un corps qui bouge, sent, expérimente, mémorise, est en relation, met en mot son expérience vivante au monde. Mais elle peut être mue, a des capteurs d'odeurs, des détecteurs de contacts, une mémoire électronique, et elle émet des phrases et des sons. Ainsi, la machine interroge les capacités de l'humain: qu'est-ce que penser ? cogiter est-il computer ? Qu’est-ce que parler : combiner des structures grammaticales et des mots disponibles dans un code donné ou tenter d’exprimer ce qui est inaccessible au regard d’autrui ? Et en second lieu, la discipline propose un questionnement sur l’organisation sociale comme machine. L’intégration des technologies de l’information dans les organisations est un cas de figure intéressant. Le travail est profondément bouleversé dans son organisation par les outils de **communication** disponibles et le détail de ces transformations constitue la description minutieuse, entrant dans le détail de chaque cas, d’une société de l’information que le chercheur oblige à se révéler comme réalité technique et économique.

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so that long term loans have a more attractive rate of interest than short loans, long term loans will be zero when assets are positive in period zero, as the following proposition demon[r]

that the constraints on variables which I will propose are often of such a complex nature that to state them as constraints on rules in par- ticular languages wo[r]

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—One of the standard mantras of the AdS=CFT correspondence is that a global symmetry of the boundary CFT is dual to a gauge symmetry of the bulk quantum gravity theory [24].. Upon furthe[r]

17.6 **Constraints** over Lattices and Hierarchical Trees
Proposals for higher computation domains have been made recently which deserve atten- tion. These include the generalization of existing interval based approaches to propose a generic framework for defining and solving interval **constraints** on any set of domains (fi- nite or infinite) that are lattices [30]. The approach is based on the use of a single form of constraint similar to that of an indexical used by Constraint Logic Programming for finite domains and on a particular generic definition of an interval domain built from an arbi- trary lattice. They provide the theoretical foundations for this framework and a schematic procedure for the operational semantics. Examples are provided that illustrate how new (compound) constraint solvers can be constructed from existing solvers using lattice com- binators and how different solvers (possibly on distinct domains) can communicate and hence, cooperate in solving a problem.

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L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignemen[r]

In different context, Che and Gale (1998), Lewis and Sappington (2000) and Thomas (2002) study mechanism design problems with finan- cial **constraints**. Like in this paper, the addition of financial **constraints** to the standard informational **constraints** modifies both the outcome and the nature of the optimal mechanism. For example, Lewis and Sappington (2000) consider privatizations to wealth-constrained operators where the most efficient operator is not necessarily the one who has the largest resources. Hence, privatization through an auction is not ex post efficient. The financial constraint modifies both the shape of the optimal mechanism and the amount (or the timing) of trade. It is optimal to limit the operator’s stake in the privatized firm to achieve an ex post efficient privatization. Thomas (2002) considers the problem of selling a good to buyers with both unknown will- ingness to pay (informational constraint) and known ability to pay (financial constraint). In the financially constrained selling mechan- ism, price discrimination is no longer optimal for high valuation buyers. Like in this paper, bunching appears in the financially constrained mechanism. However in Thomas (2002), bunching always occurs while it is not necessarily the case in this paper.

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Unité de recherche INRIA Lorraine LORIA, Technopôle de Nancy-Brabois - Campus scientifique 615, rue du Jardin Botanique - BP 101 - 54602 Villers-lès-Nancy Cedex France Unité de recherche[r]

5 https://github.com/MiniZinc/minizinc-benchmarks/blob/master/jobshop2
Furthermore, we illustrated this concept on the C UMULATIVE
constraint, which may involve numerous variables over large dimen- sions, but where only a reasonable amount of variables may be close to each others. Preliminary results show the interest of such approach for solving large scale problems and to capture local phenomena. Fu- ture work may extend this experimental study to packing **constraints**. Moreover, it would be interesting to investigate the benefit of our framework within a Large Neighborhood Search (LNS) [13], which is a common approach to solve large optimization problems. Presum- ably, self-decomposition should enable to skip most fixed variables, hence bring a significant improvement in runtime.

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objet,
c’est
à
dire
que
le
contenu
des
documents
administratifs,
il
la
voit
comme
un
processus
de
**communication**
qui
incite
surtout
la
réaction
des
récepteurs.
Son
point
de
vu
se
rapproche
de
celui
de
Dominique
Bessières
que
nous
avons
mentionné
plus
haut,
il
est
certes
intéressant
de
souligner
la
caractéristique
interactive
de
l’information
publique.
Néanmoins,
nous
pensons
que
cette
définition
n’est
pas
assez
explicite
sur
la
nature
de
l’information
publique.
En
effet,
on
dénonce
un
caractère
incertain
de
la
notion
de
l’information
publique
(BOISNIER-‐ Bardou
&
Pailliart,
2012).
Sylvie
Boisnier-‐Bardou
est
maître
de
conférence
en
Sciences
de
l’information
et
de
la
**communication**
à
l’université
Blaise
Pascal,
Isabelle
Pailliart
est
chercheure
et
enseignante
en
science
de
l’information
et
de
la
**communication**
au
sein
du
GRESEC.
D’après
les
deux
auteurs,
la
notion
de
l’information
publique
est
très
complexe,
prenons
le
cas
du
fait
qu’il
existe
des
appellations
différentes
pour
décrire
l’information
publique.
On
trouve
le
terme
d’«
information
publique
»,
mais
également
celui
de
«
donnée
publique
»,
les
deux
termes
sont
synonymes
et
en
même
temps
différents
:
le
terme
«
donnée
»
met
plutôt
l’accent
sur
la
numérisation
des
informations 6 .
De
plus,
selon
les
deux
auteurs,
les
textes

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