31,828 research outputs found
Statistical Modelling of Information Sharing: Community, Membership and Content
File-sharing systems, like many online and traditional information sharing
communities (e.g. newsgroups, BBS, forums, interest clubs), are dynamical
systems in nature. As peers get in and out of the system, the information
content made available by the prevailing membership varies continually in
amount as well as composition, which in turn affects all peers' join/leave
decisions. As a result, the dynamics of membership and information content are
strongly coupled, suggesting interesting issues about growth, sustenance and
stability.
In this paper, we propose to study such communities with a simple statistical
model of an information sharing club. Carrying their private payloads of
information goods as potential supply to the club, peers join or leave on the
basis of whether the information they demand is currently available.
Information goods are chunked and typed, as in a file sharing system where
peers contribute different files, or a forum where messages are grouped by
topics or threads. Peers' demand and supply are then characterized by
statistical distributions over the type domain.
This model reveals interesting critical behaviour with multiple equilibria. A
sharp growth threshold is derived: the club may grow towards a sustainable
equilibrium only if the value of an order parameter is above the threshold, or
shrink to emptiness otherwise. The order parameter is composite and comprises
the peer population size, the level of their contributed supply, the club's
efficiency in information search, the spread of supply and demand over the type
domain, as well as the goodness of match between them.Comment: accepted in International Symposium on Computer Performance,
Modeling, Measurements and Evaluation, Juan-les-Pins, France, October-200
An Algorithm to Determine Peer-Reviewers
The peer-review process is the most widely accepted certification mechanism
for officially accepting the written results of researchers within the
scientific community. An essential component of peer-review is the
identification of competent referees to review a submitted manuscript. This
article presents an algorithm to automatically determine the most appropriate
reviewers for a manuscript by way of a co-authorship network data structure and
a relative-rank particle-swarm algorithm. This approach is novel in that it is
not limited to a pre-selected set of referees, is computationally efficient,
requires no human-intervention, and, in some instances, can automatically
identify conflict of interest situations. A useful application of this
algorithm would be to open commentary peer-review systems because it provides a
weighting for each referee with respects to their expertise in the domain of a
manuscript. The algorithm is validated using referee bid data from the 2005
Joint Conference on Digital Libraries.Comment: Rodriguez, M.A., Bollen, J., "An Algorithm to Determine
Peer-Reviewers", Conference on Information and Knowledge Management, in
press, ACM, LA-UR-06-2261, October 2008; ISBN:978-1-59593-991-
PROTECT: Proximity-based Trust-advisor using Encounters for Mobile Societies
Many interactions between network users rely on trust, which is becoming
particularly important given the security breaches in the Internet today. These
problems are further exacerbated by the dynamics in wireless mobile networks.
In this paper we address the issue of trust advisory and establishment in
mobile networks, with application to ad hoc networks, including DTNs. We
utilize encounters in mobile societies in novel ways, noticing that mobility
provides opportunities to build proximity, location and similarity based trust.
Four new trust advisor filters are introduced - including encounter frequency,
duration, behavior vectors and behavior matrices - and evaluated over an
extensive set of real-world traces collected from a major university. Two sets
of statistical analyses are performed; the first examines the underlying
encounter relationships in mobile societies, and the second evaluates DTN
routing in mobile peer-to-peer networks using trust and selfishness models. We
find that for the analyzed trace, trust filters are stable in terms of growth
with time (3 filters have close to 90% overlap of users over a period of 9
weeks) and the results produced by different filters are noticeably different.
In our analysis for trust and selfishness model, our trust filters largely undo
the effect of selfishness on the unreachability in a network. Thus improving
the connectivity in a network with selfish nodes.
We hope that our initial promising results open the door for further research
on proximity-based trust
Understanding collaboration in volunteer computing systems
Volunteer computing is a paradigm in which devices participating in a distributed environment share part of their resources to help others perform their activities. The effectiveness of this computing paradigm depends on the collaboration attitude adopted by the participating devices. Unfortunately for software designers it is not clear how to contribute with local resources to the shared environment without compromising resources that could then be required by the contributors. Therefore, many designers adopt a conservative position when defining the collaboration strategy to be embedded in volunteer computing applications. This position produces an underutilization of the devices’ local resources and reduces the effectiveness of these solutions. This article presents a study that helps designers understand the impact of adopting a particular collaboration attitude to contribute with local resources to the distributed shared environment. The study considers five collaboration strategies, which are analyzed in computing environments with both, abundance and scarcity of resources. The obtained results indicate that collaboration strategies based on effort-based incentives work better than those using contribution-based incentives. These results also show that the use of effort-based incentives does not jeopardize the availability of local resources for the local needs.Peer ReviewedPostprint (published version
- …