213 research outputs found
Monte Carlo Methods for Top-k Personalized PageRank Lists and Name Disambiguation
We study a problem of quick detection of top-k Personalized PageRank lists.
This problem has a number of important applications such as finding local cuts
in large graphs, estimation of similarity distance and name disambiguation. In
particular, we apply our results to construct efficient algorithms for the
person name disambiguation problem. We argue that when finding top-k
Personalized PageRank lists two observations are important. Firstly, it is
crucial that we detect fast the top-k most important neighbours of a node,
while the exact order in the top-k list as well as the exact values of PageRank
are by far not so crucial. Secondly, a little number of wrong elements in top-k
lists do not really degrade the quality of top-k lists, but it can lead to
significant computational saving. Based on these two key observations we
propose Monte Carlo methods for fast detection of top-k Personalized PageRank
lists. We provide performance evaluation of the proposed methods and supply
stopping criteria. Then, we apply the methods to the person name disambiguation
problem. The developed algorithm for the person name disambiguation problem has
achieved the second place in the WePS 2010 competition
WiFly: experimenting with Wireless Sensor Networks and Virtual coordinates
Experimentation is important when designing communication protocols for
Wireless Sensor Networks. Lower-layers have a major impact on upper-layer
performance, and the complexity of the phenomena can not be entirely captured
by analysis or simulation. In this report, we go through the complete process,
from designing an energy-efficient self-organizing communication architecture
(MAC, routing and application layers) to real-life experimentation roll-outs.
The presented communication architecture includes a MAC protocol which avoids
building and maintaining neighborhood tables, and a geographically-inspired
routing protocol over virtual coordinates. The application consists of a mobile
sink interrogating a wireless sensor network based on the requests issued by a
disconnected base station. After the design process of this architecture, we
verify it functions correctly by simulation, and we perform a temporal
verification. This study is needed to calculate the maximum speed the mobile
sink can take. We detail the implementation, and the results of the off-site
experimentation (energy consumption at PHY layer, collision probability at MAC
layer, and routing). Finally, we report on the real-world deployment where we
have mounted the mobile sink node on a radio-controlled airplane
Telex: Principled System Support for Write-Sharing in Collaborative Applications
The Telex system is designed for sharing mutable data in a distributed
environment, particularly for collaborative applications. Users operate on
their local, persistent replica of shared documents; they can work disconnected
and suffer no network latency. The Telex approach to detect and correct
conflicts is application independent, based on an action-constraint graph (ACG)
that summarises the concurrency semantics of applications. The ACG is stored
efficiently in a multilog structure that eliminates contention and is optimised
for locality. Telex supports multiple applications and multi-document updates.
The Telex system clearly separates system logic (which includes replication,
views, undo, security, consistency, conflicts, and commitment) from application
logic. An example application is a shared calendar for managing multi-user
meetings; the system detects meeting conflicts and resolves them consistently
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