The
Renaissance of
Decentralized Systems 
Decentralized
systems are
symmetric distributed systems, where each participating node can in
principle
assume any of the required tasks. Such systems have enjoyed tremendous
interest
in recent years, sparked by the fact that decentralization is an
enabler for
new paradigms like cooperative computing (e.g., peer-to-peer systems),
ad hoc
networking applications, and highly resilient network services.
These
application domains
present formidable new challenges to decentralized system design.
Practical
systems must be self-organizing and extend to planetary scale. They
must
tolerate heterogeneity, dynamic membership and mobility. And, they must
provide
provable guarantees and consistency despite complex, correlated
failures, mutual
suspicion, lack of trusted authorities, and selfish or malicious
participants.
In this talk,
I will
outline the state-of-the-art in modern decentralized system design,
sketch
existing and future applications and identify key challenges that
remain.
About the speaker:
Peter
Druschel is
scientific director at the Max Planck Institute for Software Systems in
Kaiserslautern and Saarbruecken,
Previously,
he was a
Professor of Computer Science and Electrical and Computer Engineering
at
His
research interests
include distributed systems and operating systems. Peter's current work
centers
around resilient, large-scale, decentralized services and applications
in
cooperative and ad hoc environments.
He
is the recipient of an NSF CAREER award and an Alfred P. Sloan
Fellowship.
Data
Management for
Christian S. Jensen, Department of Computer Science,
We are reaching the unique point in history where a global computing and information infrastructure will emerge that supports the delivery of location-enabled services to mobile users always and everywhere, including services that rely on the tracking of the continuously changing positions of entire populations of mobile-service users. Qualitatively new services will become available that either make little sense or are of limited interest in the traditional context of fixed-location, desktop-based computing.
Following a coverage of underlying drivers and example applications, this talk describes an approach to tracking that offer accuracy guarantees for the positions of the moving objects as stored on the server side. In this approach, the server and each mobile client share a representation of the client's changing position, and each client issues an update to the server when its position as given by this shared representation deviates from its GPS position by more than a certain threshold.
A key issue is how to represent the changing position of a moving object so that tracking can be done with as few updates as possible. A range of techniques are described that utilize progressively more information about an object's movement, ranging from assuming that an object remains in its most recently reported position to assuming that past movement trajectories of an object through a road network are known. The talk reports on experimental evaluations of the tracking techniques based on real GPS data and a corresponding real road network.
Users typically have small screens and no standard keyboard, and they are engaged in some primary activity such as driving safely. For these and other reasons, it is important to deliver the ``right'' service at the right time, with minimal user interaction. This may be achieved by making services context aware. A route-aware service may suggest points of interest near the user's route, rather than merely to the user's current location. This talk describes key techniques underlying a software component that builds routes for individual users, with associated usage data, based on traces of GPS coordinates, so that the likely route(s) for a user can be identified and used in mobile services without user interaction.
About the speaker:
Christian
S. Jensen,
Ph.D., Dr.Techn., is a Professor of Computer Science at Aalborg
University,
Denmark, an Honorary Professor at Cardiff University, UK, and an
adjunct
Professor at Agder University College Norway.
His
research concerns
data management and spans issues of semantics, modeling, and
performance. With
his colleagues, he receives substantial national and international
funding for
his research, and he has authored or coauthored more than 150
scientific
papers. He is a member of the
His
service record
includes the editorial boards of ACM TODS, IEEE TKDE and the IEEE Data
Engineering Bulletin. He was the general chair of the 1995
International
Workshop on Temporal Databases and a vice program committee chair for
ICDE 1998.
He was program committee chair or co-chair fore Workshop on
Spatio-Temporal
Database Management, held with VLDB 1999, for SSTD 2001, EDBT 2002, and
VLDB
2005. He serves on the boards of directors and advisors for a small
number of
companies, and he serves regularly as a consultant.
Applying components / frameworks to the
ObjectWeb Persistence Support
(abstract not
available).
About
the speaker:
Pascal Déchamboux , Ph.D., is a senior architect at the research centre of France Telecom.
His research work concerns middleware support
for telecommunication
service delivery environment. He has been the manager for several years
of
research team that focuses on two main middleware topics:
- work on component support that lead to the proposition of the Fractal
component model and its Julia implementation, complemented with
management
capabilities.
- work on persistence support that lead to the proposition of several
frameworks such as mapping subsystem managing typed I/Os (e.g., O/R
mapping),
transactional data manager, cache manager or concurrency manager, for
building
persistence supports complying with different standards like EJB or JDO.
He has been involved in many national and international collaborative
projects,
especially with Bull and INRIA. He is one of the co-founders of the
ObjectWeb
open source community within which results of the previously mentioned
works
can be found and used with no restriction!