27 research outputs found
Simulating social relations in multi-agent systems
Open distributed systems are comprised of a large number of heterogeneous nodes with disparate requirements and objectives, a number of which may not conform to the system specification. This thesis argues that activity in such systems can be regulated by using distributed mechanisms inspired by social science theories regarding similarity /kinship, trust, reputation, recommendation and economics. This makes it possible to create scalable and robust agent societies which can adapt to overcome structural impediments and provide inherent defence against malicious and incompetent action, without detriment to system functionality and performance.
In particular this thesis describes:
• an agent based simulation and animation platform (PreSage), which offers the agent developer and society designer a suite of powerful tools for creating, simulating and visualising agent societies from both a local and global perspective.
• a social information dissemination system (SID) based on principles of self organisation which personalises recommendation and directs information dissemination.
• a computational socio-cognitive and economic framework (CScEF) which integrates and extends socio-cognitive theories of trust, reputation and recommendation with basic economic theory.
• results from two simulation studies investigating the performance of SID and the CScEF.
The results show the production of a generic, reusable and scalable platform for developing and animating agent societies, and its contribution to the community as an open source tool. Secondly specific results, regarding the application of SID and CScEF, show that revealing outcomes of using socio-technical mechanisms to condition agent interactions can be demonstrated and identified by using Presage.Open Acces
A Transparent, Reputation-Based Architecture for Semantic Web Annotation
New forms of conceiving the web such as web 2.0 and the semantic web have
emerged for numerous purposes ranging from professional activities to leisure.
The semantic web is based on associating concepts with web pages, rather than
only identifying hyperlinks and repeated literals. ITACA is a project whose aim
is to add semantic annotations to web pages, where semantic annotations are
Wikipedia URLs. Therefore, users can write, read and vote on semantic annotations
of a webpage. Semantic annotations of a webpage are ranked according
to users' votes. Building upon the ITACA project, we propose a transparent,
reputation-based architecture. With this proposal, semantic annotations are
stored in the users' local machines instead of web servers, so that web servers
transparency is preserved. To achieve transparency, an indexing server is added
to the architecture to locate semantic annotations. Moreover, users are grouped
into reputation domains, providing accurate semantic annotation ranking when
retrieving annotations of a web page. Cache copies of semantic annotations in
annotation servers are done to improve eficiency of the algorithm, reducing the
number of sent messages
Recent Developments on Mobile Ad-Hoc Networks and Vehicular Ad-Hoc Networks
This book presents collective works published in the recent Special Issue (SI) entitled "Recent Developments on Mobile Ad-Hoc Networks and Vehicular Ad-Hoc Networks”. These works expose the readership to the latest solutions and techniques for MANETs and VANETs. They cover interesting topics such as power-aware optimization solutions for MANETs, data dissemination in VANETs, adaptive multi-hop broadcast schemes for VANETs, multi-metric routing protocols for VANETs, and incentive mechanisms to encourage the distribution of information in VANETs. The book demonstrates pioneering work in these fields, investigates novel solutions and methods, and discusses future trends in these field
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Computational models of trust for cooperative evolution. Reputation based game theoretic models of trust for cooperative evolution in online business games.
Online services such as e-marketplaces, social networking sites, online gaming environments etc have grown in popularity in the recent years. These services represent situation where participants do not get to negotiate face to face before interaction and most of the time parties to transaction remain anonymous. It is thus necessary to have a system that rightly assesses trustworthiness of the other party in order to maintain quality assurance in such systems. Recent works on Trust and Reputation in online communities have focused on identifying probable defaulters, but less effort has been put to come up with system that make cooperation attractive over defection in order to achieve cooperation without enforcement. Our work in this regard concerns design and investigation of trust assessment systems that not only filter defaulters but also promote evolution of cooperativeness in player society.
Based on the concept of game theory and prisonerÂżs dilemma, we model business games and design incentive method, compensation method, acquaintance based assessment method and decision theoretic assessment method as mechanisms to assure trustworthiness in online business environments. Effectiveness of each of these methods in promoting the evolution of cooperation in player society has been investigated. Our results show that these methods contribute positively in promoting cooperative evolution.
We have further extended our trust assessment model to suit the needs of a mobile ad-hoc network setting. The effectiveness of this model has been tested against its capability to reduce packet drop rate and energy conservation. In both of these the results show promise.EU Asia-link project TH/Asia Link/004(91712) East-West and its local host Kantipur Engineering College in Nepal, and Kathmandu University
A Transparent, Reputation-Based Architecture for Semantic Web Annotation
New forms of conceiving the web such as web 2.0 and the semantic web have
emerged for numerous purposes ranging from professional activities to leisure.
The semantic web is based on associating concepts with web pages, rather than
only identifying hyperlinks and repeated literals. ITACA is a project whose aim
is to add semantic annotations to web pages, where semantic annotations are
Wikipedia URLs. Therefore, users can write, read and vote on semantic annotations
of a webpage. Semantic annotations of a webpage are ranked according
to users' votes. Building upon the ITACA project, we propose a transparent,
reputation-based architecture. With this proposal, semantic annotations are
stored in the users' local machines instead of web servers, so that web servers
transparency is preserved. To achieve transparency, an indexing server is added
to the architecture to locate semantic annotations. Moreover, users are grouped
into reputation domains, providing accurate semantic annotation ranking when
retrieving annotations of a web page. Cache copies of semantic annotations in
annotation servers are done to improve eficiency of the algorithm, reducing the
number of sent messages
Systems for Challenged Network Environments.
Developing regions face significant challenges in network access, making even simple network tasks unpleasant and rich media prohibitively difficult to access. Even as cellular network coverage is approaching a near-universal reach, good network connectivity remains scarce and expensive in many emerging markets. The underlying theme in this dissertation is designing network systems that better accommodate users in emerging markets. To do so, this dissertation begins with a nuanced analysis of content access behavior for web users in developing regions. This analysis finds the personalization of content access---and the fragmentation that results from it---to be significant factors in undermining many existing web acceleration mechanisms. The dissertation explores content access behavior from logs collected at shared internet access sites, as well as user activity information obtained from a commercial social networking service with over a hundred million members worldwide.
Based on these observations, the dissertation then discusses two systems designed for improving end-user experience in accessing and using content in constrained networks. First, it deals with the challenge of distributing private content in these networks. By leveraging the wide availability of cellular telephones, the dissertation describes a system for personal content distribution based on user access behavior. The system enables users to request future data accesses, and it schedules content transfers according to current and expected capacity. Second, the dissertation looks at routing bulk data in challenged networks, and describes an experimentation platform for building systems for challenged networks. This platform enables researchers to quickly prototype systems for challenged networks, and iteratively evaluate these systems using mobility and network emulation. The dissertation describes a few data routing systems that were built atop this experimentation platform.
Finally, the dissertation discusses the marketplace and service discovery considerations that are important in making these systems viable for developing-region use. In particular, it presents an extensible, auction-based market platform that relies on widely available communication tools for conveniently discovering and trading digital services and goods in developing regions. Collectively, this dissertation brings together several projects that aim to understand and improve end-user experience in challenged networks endemic to developing regions.Ph.D.Computer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91401/1/azarias_1.pd
Enhancing trustability in MMOGs environments
Massively Multiplayer Online Games (MMOGs; e.g., World of Warcraft), virtual worlds
(VW; e.g., Second Life), social networks (e.g., Facebook) strongly demand for more
autonomic, security, and trust mechanisms in a way similar to humans do in the real
life world. As known, this is a difficult matter because trusting in humans and organizations
depends on the perception and experience of each individual, which is difficult to
quantify or measure. In fact, these societal environments lack trust mechanisms similar
to those involved in humans-to-human interactions. Besides, interactions mediated
by compute devices are constantly evolving, requiring trust mechanisms that keep the
pace with the developments and assess risk situations.
In VW/MMOGs, it is widely recognized that users develop trust relationships from their
in-world interactions with others. However, these trust relationships end up not being
represented in the data structures (or databases) of such virtual worlds, though they
sometimes appear associated to reputation and recommendation systems. In addition,
as far as we know, the user is not provided with a personal trust tool to sustain his/her
decision making while he/she interacts with other users in the virtual or game world.
In order to solve this problem, as well as those mentioned above, we propose herein a
formal representation of these personal trust relationships, which are based on avataravatar
interactions. The leading idea is to provide each avatar-impersonated player
with a personal trust tool that follows a distributed trust model, i.e., the trust data is
distributed over the societal network of a given VW/MMOG.
Representing, manipulating, and inferring trust from the user/player point of view certainly
is a grand challenge. When someone meets an unknown individual, the question
is “Can I trust him/her or not?”. It is clear that this requires the user to have access to
a representation of trust about others, but, unless we are using an open source VW/MMOG,
it is difficult —not to say unfeasible— to get access to such data. Even, in an open
source system, a number of users may refuse to pass information about its friends, acquaintances,
or others. Putting together its own data and gathered data obtained from
others, the avatar-impersonated player should be able to come across a trust result
about its current trustee. For the trust assessment method used in this thesis, we use
subjective logic operators and graph search algorithms to undertake such trust inference
about the trustee. The proposed trust inference system has been validated using
a number of OpenSimulator (opensimulator.org) scenarios, which showed an accuracy
increase in evaluating trustability of avatars.
Summing up, our proposal aims thus to introduce a trust theory for virtual worlds, its
trust assessment metrics (e.g., subjective logic) and trust discovery methods (e.g.,
graph search methods), on an individual basis, rather than based on usual centralized
reputation systems. In particular, and unlike other trust discovery methods, our methods
run at interactive rates.MMOGs (Massively Multiplayer Online Games, como por exemplo, World of Warcraft),
mundos virtuais (VW, como por exemplo, o Second Life) e redes sociais (como por exemplo,
Facebook) necessitam de mecanismos de confiança mais autónomos, capazes de
assegurar a segurança e a confiança de uma forma semelhante à que os seres humanos
utilizam na vida real. Como se sabe, esta não é uma questão fácil. Porque confiar em
seres humanos e ou organizações depende da percepção e da experiĂŞncia de cada indivĂduo,
o que Ă© difĂcil de quantificar ou medir Ă partida. Na verdade, esses ambientes
sociais carecem dos mecanismos de confiança presentes em interacções humanas presenciais.
Além disso, as interacções mediadas por dispositivos computacionais estão em
constante evolução, necessitando de mecanismos de confiança adequados ao ritmo da
evolução para avaliar situações de risco.
Em VW/MMOGs, é amplamente reconhecido que os utilizadores desenvolvem relações
de confiança a partir das suas interacções no mundo com outros. No entanto, essas relações
de confiança acabam por não ser representadas nas estruturas de dados (ou bases
de dados) do VW/MMOG especĂfico, embora Ă s vezes apareçam associados Ă reputação
e a sistemas de reputação. Além disso, tanto quanto sabemos, ao utilizador não lhe
é facultado nenhum mecanismo que suporte uma ferramenta de confiança individual
para sustentar o seu processo de tomada de decisĂŁo, enquanto ele interage com outros
utilizadores no mundo virtual ou jogo. A fim de resolver este problema, bem como
os mencionados acima, propomos nesta tese uma representação formal para essas relações
de confiança pessoal, baseada em interacções avatar-avatar. A ideia principal
é fornecer a cada jogador representado por um avatar uma ferramenta de confiança
pessoal que segue um modelo de confiança distribuĂda, ou seja, os dados de confiança
sĂŁo distribuĂdos atravĂ©s da rede social de um determinado VW/MMOG.
Representar, manipular e inferir a confiança do ponto de utilizador/jogador, é certamente
um grande desafio. Quando alguĂ©m encontra um indivĂduo desconhecido, a
pergunta é “Posso confiar ou não nele?”. É claro que isto requer que o utilizador tenha
acesso a uma representação de confiança sobre os outros, mas, a menos que possamos
usar uma plataforma VW/MMOG de cĂłdigo aberto, Ă© difĂcil — para nĂŁo dizer impossĂvel
— obter acesso aos dados gerados pelos utilizadores. Mesmo em sistemas de código
aberto, um número de utilizadores pode recusar partilhar informações sobre seus amigos,
conhecidos, ou sobre outros. Ao juntar seus prĂłprios dados com os dados obtidos de
outros, o utilizador/jogador representado por um avatar deve ser capaz de produzir uma
avaliação de confiança sobre o utilizador/jogador com o qual se encontra a interagir.
Relativamente ao método de avaliação de confiança empregue nesta tese, utilizamos
lógica subjectiva para a representação da confiança, e também operadores lógicos da
lĂłgica subjectiva juntamente com algoritmos de procura em grafos para empreender
o processo de inferência da confiança relativamente a outro utilizador. O sistema de
inferência de confiança proposto foi validado através de um número de cenários Open-Simulator (opensimulator.org), que mostrou um aumento na precisão na avaliação da
confiança de avatares.
Resumindo, a nossa proposta visa, assim, introduzir uma teoria de confiança para mundos
virtuais, conjuntamente com métricas de avaliação de confiança (por exemplo, a
lógica subjectiva) e em métodos de procura de caminhos de confiança (com por exemplo,
através de métodos de pesquisa em grafos), partindo de uma base individual, em
vez de se basear em sistemas habituais de reputação centralizados. Em particular, e ao
contrário de outros métodos de determinação do grau de confiança, os nossos métodos
sĂŁo executados em tempo real