|
 Mi, 23.11.2005
|
Prof. Dr. Christian Scheideler
Towards a paradigm for robust distributed algorithms and data structures
|
|
There is a wealth of literature on distributed algorithms and data
structures.
Standard models used in the research community are synchronous or
asynchronous
shared memory or network models. The shared memory model is basically a
generalization of the von Neumann model from one processing unit to
multiple
processing units or processes acting on a single, linear addressable
memory. In
the network model, there is no shared memory. Every processing unit has
its
own, private memory, and the processing units are connected by a network
of
(usually) bidirectional communication links that allow the processing
units to
exchange messages. The set of processing units is usually considered to
be
fixed though processing units may fail and recover according to some
stochastic
or adversarial model.
With the rise of very large distributed systems such as peer-to-peer
systems,
these models are not appropriate any more. For example, the set of
processing
units can be highly dynamic and there may not be any mutual trust
relationships
between the units. This creates fundamental problems, such as keeping
the
(honest) units in a single connected component, that the previous models
cannot
address in their basic form. We show how to extend the network model so
that we
have a model that is powerful enough to design algorithms and data
structures
that are provably robust even against massive adversarial attacks. This
model
even allows to design strategies capable of addressing modern threats
such as
denial-of-service attacks and phishing that appear to lie outside of the
algorithms domain.
|
|
|
Mi, 30.11.2005
|
|
|
Mi, 07.12.2005
|
|
|
Mi, 14.12.2005
|
Stefan Pfingstl
Projekt FIS-I --- Das Portal www.io-port.net
|
|
Im Projekt FIS-I wurde ein Web-Portal zur Literaturrecherche im Bereich der Informatik erstellt.
Die Daten verschiedener Anbieter wurden in einer zentralen Datenbank zusammengefasst und
mit Hilfe von traditionellen und neu entwickelten sematischen Methoden wird der Benutzer
bei der Suche nach relavanter Literatur unterstützt.
|
|
|
Mi, 21.12.2005
|
|
|
Mi, 11.01.2006
|
|
|
Mi, 18.01.2006
|
Dr. Christoph Flamm, Universität Leipzig
ALGEBRAIC COMPARISON OF METABOLIC NETWORKS
|
|
Many methods for the comparison of metabolic networks of
different organisms are based on gene content. Mis-annotation
of orthologous genes and functional replacement of genes pose
a major problem for these approaches, since the phylogenetic
information contained in the metabolic networks themselves is
completely neglected.
A new approach based on well-known operations from set algebra
and their application to the direct comparison of metabolic
networks will be presented which circumvents the problems described
above. Phylogenies constructed in that way are in good agreement
with those constructed from other data sources like 16S RNA.
|
|
|
Mi, 25.01.2006
|
Dmytro Chibisov
Generation of Quasi-Orthogonal Grids On Curvilinear Trimmed Regions With
Moving Boundaries
|
|
We propose a new algorithm for the generation of quasiorthogonal grids on regions bounded
by arbitrary number of polynomial inequalities. Instead of calculation of the grid nodes
positions and corresponding line segments for a particular region, we perform
all calculations for general polynomials of bounded degree given with indeterminate coefficients.
The first advantage of this approach is that the calculations can be performed only once
and then used to generate grids on regions with moving boundaries and of arbitrary
mesh size with constant computational costs. The second advantage of our algorithm
is the avoidance of singularities, which occur while using the existing algebraic grid
generation methods and lead to the intersection of grid lines.
|
|
|
Mi, 08.02.2006
|
|
