37 research outputs found
Representing Conversations for Scalable Overhearing
Open distributed multi-agent systems are gaining interest in the academic
community and in industry. In such open settings, agents are often coordinated
using standardized agent conversation protocols. The representation of such
protocols (for analysis, validation, monitoring, etc) is an important aspect of
multi-agent applications. Recently, Petri nets have been shown to be an
interesting approach to such representation, and radically different approaches
using Petri nets have been proposed. However, their relative strengths and
weaknesses have not been examined. Moreover, their scalability and suitability
for different tasks have not been addressed. This paper addresses both these
challenges. First, we analyze existing Petri net representations in terms of
their scalability and appropriateness for overhearing, an important task in
monitoring open multi-agent systems. Then, building on the insights gained, we
introduce a novel representation using Colored Petri nets that explicitly
represent legal joint conversation states and messages. This representation
approach offers significant improvements in scalability and is particularly
suitable for overhearing. Furthermore, we show that this new representation
offers a comprehensive coverage of all conversation features of FIPA
conversation standards. We also present a procedure for transforming AUML
conversation protocol diagrams (a standard human-readable representation), to
our Colored Petri net representation
Integrated Social and Quality of Service Trust Management of Mobile Groups in Ad Hoc Networks
Abstract—We propose to combine social trust derived from social networks with quality-of-service (QoS) trust derived from communication networks to obtain a composite trust metric as a basis for evaluating trust of mobile nodes in mobile ad hoc network (MANET) environments. We develop a novel modelbased approach to identify the best protocol setting under which trust bias is minimized, that is, the peer-to-peer subjective trust as a result of executing our distributed trust management protocol is close to ground truth status over a wide range of operational and environment conditions with high resiliency to malicious attacks and misbehaving nodes. Keywords—trust management; mobile ad hoc networks; QoS trust; social trust; trust bias minimization. I
Petri Net Plans A framework for collaboration and coordination in multi-robot systems
Programming the behavior of multi-robot systems is a challenging task which has a key role in developing effective systems in many application domains. In this paper, we present Petri Net Plans (PNPs), a language based on Petri Nets (PNs), which allows for intuitive and effective robot and multi-robot behavior design. PNPs are very expressive and support a rich set of features that are critical to develop robotic applications, including sensing, interrupts and concurrency. As a central feature, PNPs allow for a formal analysis of plans based on standard PN tools. Moreover, PNPs are suitable for modeling multi-robot systems and the developed behaviors can be executed in a distributed setting, while preserving the properties of the modeled system. PNPs have been deployed in several robotic platforms in different application domains. In this paper, we report three case studies, which address complex single robot plans, coordination and collaboration
Debugging multi-agent systems with design documents
Debugging multi-agent systems, which are concurrent, distributed, and consist of complex components is difficult, yet crucial. The development of these complex systems is supported by agent-oriented software engineering methodologies which utilise agents as the central design metaphor. The systems that are developed are inherently complex since the components of these systems may interact in flexible and sophisticated ways and traditional debugging techniques are not appropriate. Despite this, very little effort has been applied to developing appropriate debugging tools and techniques. Debugging multi-agent systems without good debugging tools is highly impractical and without suitable debugging support developing and maintaining multi-agent systems will be more difficult than it need be. In this thesis we propose that the debugging process can be supported by following an agent-oriented design methodology, and then using the developed design artifacts in the debugging phase. We propose a domain independent debugging framework which comprises the developed processes and components that are necessary in using design artifacts as debugging artifacts. Our approach is to take a non-formal design artifact, such as an AUML protocol design, and encode it in a machine interpretable manner such that the design can be used as a model of correct system behaviour. These models are used by a run-time debugging system to compare observed behaviour against specified behaviour. We provide details for transforming two design artifact types into equivalent debugging artifacts and show how these can be used to detect bugs. During a debugging episode in which a bug has been identified our debugging approach can provide detailed information about the possible reason for the bug occurring. To determine if this information was useful in helping to debug programs we undertook a thorough empirical study and identified that use of the debugging tool translated to an improvement in debugging performance. We conclude that the debugging techniques developed in this thesis provide effective debugging support for multi-agent systems and by having an extensible framework new design artifacts can be explored and as translations are developed they can be added to the debugging system
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Distributed Termination Detection For Multiagent Protocols
The research conducted in this thesis is on distributed termination detection in multiagent systems.
Agents engage in complex interactions by executing behaviour specifications in the form of protocols. This work presents and experiments with a framework for making termination in a multiagent system explicit. As a side effect, the mechanism can be exploited to aid management of agent interactions, by providing visibility of the interaction process and can be extended to drive multiagent system management tasks such as timely garbage collection.
Results from previous attempts to deploy agents systems when scaling up, e.g. Agentcities, have shown and exposed a big gap between theory and practice especially in the reliability and availability of deployed systems. In particular more work needs to be done in the area of supporting agent infrastructures as much as in theoretical agent foundations.
There are two aspects to this problem of termination detection in multiagent systems, firstly, the formal verification of behaviour at compile-time and secondly, monitoring and control at run-time. Regarding the former, there has been some work on the ver- 13 ification of agent communication languages. But overall verification is difficult and often requires knowledge of internal states of agents at compile time, and as yet has not been satisfactorily solved to be deployed in real systems. The second, the runtime approach is adopted in here.
The research is not about protocol engineering but assumes correct protocols, and protocol specifications to be finite state machine graphs. Given these correct verified protocols, the thesis proposes a number of definitions culminating in identification of minimal information in the form of sub-protocols that agents being autonomous, can make available for the termination detection. An off line procedure for deriving these sub-protocols is then presented.
The thesis then considers a termination detection model, and within this model, proposes an conversationmodel encompassing protocol executions, with hierarchical conversations modelled as diffusing computation trees and defines a number of predicates to derive termination in centralised and distributed environments. Algorithms that implement these predicates are sketched and some complexity analysis is performed. The thesis then considers a prototype implementation evaluated over some defined detection delays metric.
The evaluation approach is heavily empirical, with an experimental approach adopted to evaluate various configurations of the termination detection mechanism. The evaluation employs robust resampling and bootstrapping methods to analyse and obtain distributions and confidence intervals of the detection delays metric for the termination detection mechanism
Energy Efficiency inWireless Sensor Networks: Transmission Protocols and Performance Evaluation
Doktorgradsavhandling, Fakultet for teknologi og realfag, Universitetet i Agder, 2016Energy efficiency is one of the major goals for achieving green wireless communications.
The recent growth in ubiquitous wireless connections and multimedia
applications demands higher energy efficiency for wireless communications.
As a part of this picture, wireless sensor networks (WSNs) need to
be more energy efficient since the battery capacity of nodes in such networks
is limited in the absence of energy harvesting sources.
In general, an energy efficient protocol should perform as few as possible
operations when delivering user information successfully across the network.
Energy efficient data transmission schemes could utilize network resources
more effectively to lower down the energy consumption level. In this dissertation
research, we focus on improving energy efficiency for data transmission
and medium access control (MAC) protocols in WSNs. While energy consumption
is inevitable for transmitting and receiving data in a WSN, the other
typical and dominant energy consumption activities are idle listening, overhearing,
and retransmissions due to unsuccessful transmission attempts. An
energy efficient MAC protocol conserves energy by minimizing all these auxiliary
operations in order to prolong network lifetime. On the other hand, balanced
energy consumption among nodes which mitigates energy hole across
a WSN also helps to extend network lifetime.
In this context, we propose two cooperative transmission (CT) based energy
balancingMAC protocols for the purpose of WSN lifetime prolongation.
The first one is an asynchronous cooperative transmission MAC protocol, in
which nodes generate their own wakeup schedules based on their level number
in a WSN topology. The second one is a receiver initiated cooperative
transmission MAC protocol in which the CT is initiated by a relay node. It
is demonstrated that both proposed CT MAC protocols are able to achieve
significantly extended network lifetime.
In addition, an energy conserving sleeping mechanism for synchronous
duty cycling MAC protocols is also proposed in this thesis. It is an eventtriggered
sleeping (ETS) mechanism, which triggers the sleep mode of a node
based on the incoming traffic pattern to that node. The ETS mechanism eliminates
overhearing in a WSN and achieves higher energy efficiency.
Furthermore, we apply packet aggregation at the MAC layer in WSNs for achieving more energy efficient data transmission. In aggregated packet
transmission (APT), multiple packets are transmitted as a batch in a frame
within a single duty cycle instead of transmitting merely one packet per cycle.
Numerical results demonstrate that APT achieves higher throughput and
shorter delay, in addition to higher energy efficiency.
To evaluate the performance of the proposed MAC protocols and transmission
schemes, we develop discrete time Markov chain (DTMC) models
and verify them by comparing the results obtained from both analysis and
discrete-event based simulations. The analytical and simulation results match
precisely with each other, confirming the effectiveness of the proposed protocols
and schemes as well as the accuracy of the developed models
Using Norms To Control Open Multi-Agent Systems
Internet es, tal vez, el avance cientÃfico más relevante de nuestros dÃas. Entre
otras cosas, Internet ha permitido la evolución de los paradigmas de computación tradicionales hacia el paradigma de computaciónn distribuida, que se
caracteriza por utilizar una red abierta de ordenadores. Los sistemas multiagente
(SMA) son una tecnolog a adecuada para abordar los retos motivados
por estos sistemas abiertos distribuidos. Los SMA son aplicaciones formadas
por agentes heterog eneos y aut onomos que pueden haber sido dise~nados de
forma independiente de acuerdo con objetivos y motivaciones diferentes. Por
lo tanto, no es posible realizar ninguna hip otesis a priori sobre el comportamiento
de los agentes. Por este motivo, los SMA necesitan de mecanismos
de coordinaci on y cooperaci on, como las normas, para garantizar el orden
social y evitar la aparici on de conictos.
El t ermino norma cubre dos dimensiones diferentes: i) las normas como
un instrumento que gu a a los ciudadanos a la hora de realizar acciones y
actividades, por lo que las normas de nen los procedimientos y/o los protocolos
que se deben seguir en una situaci on concreta, y ii) las normas como
ordenes o prohibiciones respaldadas por un sistema de sanciones, por lo que
las normas son medios para prevenir o castigar ciertas acciones. En el area
de los SMA, las normas se vienen utilizando como una especi caci on formal
de lo que est a permitido, obligado y prohibido dentro de una sociedad. De
este modo, las normas permiten regular la vida de los agentes software y las
interacciones entre ellos.
La motivaci on principal de esta tesis es permitir a los dise~nadores de los
SMA utilizar normas como un mecanismo para controlar y coordinar SMA
abiertos. Nuestro objetivo es elaborar mecanismos normativos a dos niveles:
a nivel de agente y a nivel de infraestructura. Por lo tanto, en esta tesis se
aborda primero el problema de la de nici on de agentes normativos aut onomos
que sean capaces de deliberar acercaCriado Pacheco, N. (2012). Using Norms To Control Open Multi-Agent Systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17800Palanci
Classification and Comparative Study of Routing Techniques in Adhoc Wireless Networks
Wireless systems have been in use since 1980s. We have seen their evolutions to first, second and third generation's wireless systems. Wireless systems operate with the aid of a centralized supporting structure such as an access point. These access points assist the wireless users to keep connected with the wireless system, when they roam from one place to the other.
The presence of a fixed supporting structure limits the adaptability of wireless systems. In other words, the technology cannot work effectively in places where there is no fixed infrastructure. Future generation wireless systems will require easy and quick deployment of wireless networks. This quick network deployment is not possible with the Infrastructured wireless systems.
Recent advancements such as Bluetooth introduced a new type of wireless systems known as ad-hoc networks. Ad-hoc networks or "short live" networks operate in the absence of fixed infrastructure. They offer quick and easy network deployment in situations where it is not possible otherwise. Ad-hoc is a Latin word, which means "for this or for this only." Mobile ad-hoc network is an autonomous system of mobile nodes connected by wireless links; each node operates as an end system and a router for all other nodes in the network.
Nodes in ad-hoc network are free to move and organize themselves in an arbitrary fashion. Each user is free to roam about while communication with others. The path between each pair of the users may have multiple links and the radio between them can be heterogeneous. This allows an association of various links to be a part of the same network.
A mobile ad-hoc network is a collection of mobile nodes forming an ad-hoc network without the assistance of any centralized structures. These networks introduced a new art of network establishment and can be well suited for an environment where either the infrastructure is lost or where deploy an infrastructure is not very cost effective. The popular IEEE 802.11 "WI-FI" protocol is capable of providing ad-hoc network facilities at low level, when no access point is available. However in this case, the nodes are limited to send and receive information but do not route anything across the network. Ad-hoc networks can operate in a standalone fashion or could possibly be connected to a larger network such as the Internet.
An ad-hoc network has certain characteristics, which imposes new demands on the routing protocol. The most important characteristic is the dynamic topology, which is a consequence of node mobility. Nodes can change position quite frequently; the nodes in an ad-hoc network can consist of laptops and personal digital assistants and are often very limited in resources such as CPU power, storage capacity, battery power and bandwidth. This means that the routing protocol should try to minimize control traffic, such as periodic update messages. The Internet Engineering Task Force currently has a working group named Mobile Ad-hoc Networks that is working on routing specifications for ad-hoc networks. This M.Phill thesis evaluates some of the protocols put forth by the working group. This evaluation is done by means of simulation using Network simulator 2 from Berkeley.
This work aims at classification of the existing routing protocols of adhoc wireless networks using some definite parameters. After classification of routing protocols of adhoc wireless network, their comparative study was undertaken in order to yield category wise distribution. Furthermore performance evaluation of these protocols was carried out by employing different parameters like fading models, mobility models, traffic patterns etc using the network simulator NS-2
Hence I explore and evaluate different methods for validation of ad hoc routing protocols which are used to set up forwarding paths in spontaneous networks of mobile/Adhoc devices to accomplish the above mentioned comparative study and classification
Proceedings of The Multi-Agent Logics, Languages, and Organisations Federated Workshops (MALLOW 2010)
http://ceur-ws.org/Vol-627/allproceedings.pdfInternational audienceMALLOW-2010 is a third edition of a series initiated in 2007 in Durham, and pursued in 2009 in Turin. The objective, as initially stated, is to "provide a venue where: the cost of participation was minimum; participants were able to attend various workshops, so fostering collaboration and cross-fertilization; there was a friendly atmosphere and plenty of time for networking, by maximizing the time participants spent together"