66,886 research outputs found
Stable Invitations
We consider the situation in which an organizer is trying to convene an
event, and needs to choose a subset of agents to be invited. Agents have
preferences over how many attendees should be at the event and possibly also
who the attendees should be. This induces a stability requirement: All invited
agents should prefer attending to not attending, and all the other agents
should not regret being not invited. The organizer's objective is to find the
invitation of maximum size subject to the stability requirement. We investigate
the computational complexity of finding the maximum stable invitation when all
agents are truthful, as well as the mechanism design problem when agents may
strategically misreport their preferences.Comment: To appear in COMSOC 201
How people make friends in social networking sites - A microscopic perspective
We study the detailed growth of a social networking site with full temporal
information by examining the creation process of each friendship relation that
can collectively lead to the macroscopic properties of the network. We first
study the reciprocal behavior of users, and find that link requests are quickly
responded to and that the distribution of reciprocation intervals decays in an
exponential form. The degrees of inviters/accepters are slightly negatively
correlative with reciprocation time. In addition, the temporal feature of the
online community shows that the distributions of intervals of user behaviors,
such as sending or accepting link requests, follow a power law with a universal
exponent, and peaks emerge for intervals of an integral day. We finally study
the preferential selection and linking phenomena of the social networking site
and find that, for the former, a linear preference holds for preferential
sending and reception, and for the latter, a linear preference also holds for
preferential acceptance, creation, and attachment. Based on the linearly
preferential linking, we put forward an analyzable network model which can
reproduce the degree distribution of the network. The research framework
presented in the paper could provide a potential insight into how the
micro-motives of users lead to the global structure of online social networks.Comment: 10 pages, 12 figures, 2 table
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TINA as a virtual market place for telecommunication and information services: the VITAL experiment
The VITAL (Validation of Integrated Telecommunication Architectures for the Long-Term) project has defined, implemented and demonstrated an open distributed telecommunication architecture (ODTA) for deploying, managing and using a set of heterogeneous multimedia, multi-party, and mobility services. The architecture was based on the latest specifications released by TINA-C. The architecture was challenged in a set of trials by means of a heterogeneous set of applications. Some of the applications were developed within the project from scratch, while some others focused on integrating commercially available applications. The applications were selected in such a way as to assure full coverage of the architecture implementation and reflect a realistic use of it. The VITAL experience of refining and implementing TINA specifications and challenging the resulting platform by a heterogeneous set of services has proven the openness, flexibility and reusability of TINA. This paper describes the VITAL approach when choosing the different services and how they challenge and interact with the architecture, focusing especially on the service architecture and the Ret reference point definitions. The VITAL adjustments and enhancements to the TINA architecture are described. This paper contributes to proving that the TINA-based VITAL ODTA allows for easy and cost-effective development and deployment of advanced end-user and operator services, and can indeed act as the basis for a virtual market place for telecommunications service
Network formation by reinforcement learning: the long and medium run
We investigate a simple stochastic model of social network formation by the
process of reinforcement learning with discounting of the past. In the limit,
for any value of the discounting parameter, small, stable cliques are formed.
However, the time it takes to reach the limiting state in which cliques have
formed is very sensitive to the discounting parameter. Depending on this value,
the limiting result may or may not be a good predictor for realistic
observation times.Comment: 14 page
Modeling the formation of R\&D alliances: An agent-based model with empirical validation
We develop an agent-based model to reproduce the size distribution of R\&D
alliances of firms. Agents are uniformly selected to initiate an alliance and
to invite collaboration partners. These decide about acceptance based on an
individual threshold that is compared with the utility expected from joining
the current alliance. The benefit of alliances results from the fitness of the
agents involved. Fitness is obtained from an empirical distribution of agent's
activities. The cost of an alliance reflects its coordination effort. Two free
parameters and scale the costs and the individual threshold. If
initiators receive rejections of invitations, the alliance formation stops
and another initiator is selected. The three free parameters
are calibrated against a large scale data set of about 15,000 firms engaging in
about 15,000 R\&D alliances over 26 years. For the validation of the model we
compare the empirical size distribution with the theoretical one, using
confidence bands, to find a very good agreement. As an asset of our agent-based
model, we provide an analytical solution that allows to reduce the simulation
effort considerably. The analytical solution applies to general forms of the
utility of alliances. Hence, the model can be extended to other cases of
alliance formation. While no information about the initiators of an alliance is
available, our results indicate that mostly firms with high fitness are able to
attract newcomers and to establish larger alliances
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