24 research outputs found
Dynamic FTSS in Asynchronous Systems: the Case of Unison
Distributed fault-tolerance can mask the effect of a limited number of
permanent faults, while self-stabilization provides forward recovery after an
arbitrary number of transient fault hit the system. FTSS protocols combine the
best of both worlds since they are simultaneously fault-tolerant and
self-stabilizing. To date, FTSS solutions either consider static (i.e. fixed
point) tasks, or assume synchronous scheduling of the system components. In
this paper, we present the first study of dynamic tasks in asynchronous
systems, considering the unison problem as a benchmark. Unison can be seen as a
local clock synchronization problem as neighbors must maintain digital clocks
at most one time unit away from each other, and increment their own clock value
infinitely often. We present many impossibility results for this difficult
problem and propose a FTSS solution when the problem is solvable that exhibits
optimal fault containment
Probabilistic Model Checking for Energy Analysis in Software Product Lines
In a software product line (SPL), a collection of software products is
defined by their commonalities in terms of features rather than explicitly
specifying all products one-by-one. Several verification techniques were
adapted to establish temporal properties of SPLs. Symbolic and family-based
model checking have been proven to be successful for tackling the combinatorial
blow-up arising when reasoning about several feature combinations. However,
most formal verification approaches for SPLs presented in the literature focus
on the static SPLs, where the features of a product are fixed and cannot be
changed during runtime. This is in contrast to dynamic SPLs, allowing to adapt
feature combinations of a product dynamically after deployment. The main
contribution of the paper is a compositional modeling framework for dynamic
SPLs, which supports probabilistic and nondeterministic choices and allows for
quantitative analysis. We specify the feature changes during runtime within an
automata-based coordination component, enabling to reason over strategies how
to trigger dynamic feature changes for optimizing various quantitative
objectives, e.g., energy or monetary costs and reliability. For our framework
there is a natural and conceptually simple translation into the input language
of the prominent probabilistic model checker PRISM. This facilitates the
application of PRISM's powerful symbolic engine to the operational behavior of
dynamic SPLs and their family-based analysis against various quantitative
queries. We demonstrate feasibility of our approach by a case study issuing an
energy-aware bonding network device.Comment: 14 pages, 11 figure
Dynamic FTSS in Asynchronous Systems: the Case of Unison
Distributed fault-tolerance can mask the effect of a limited number of permanent faults, while self-stabilization provides forward recovery after an arbitrary number of transient fault hit the system. FTSS protocols combine the best of both worlds since they are simultaneously fault-tolerant and self-stabilizing. To date, FTSS solutions either consider static (i.e. fixed point) tasks, or assume synchronous scheduling of the system components. In this paper, we present the first study of dynamic tasks in asynchronous systems, considering the unison problem as a benchmark. Unison can be seen as a local clock synchronization problem as neighbors must maintain digital clocks at most one time unit away from each other, and increment their own clock value infinitely often. We present many impossibility results for this difficult problem and propose a FTSS solution when the problem is solvable that exhibits optimal fault containment
Self-Stabilizing Byzantine Asynchronous Unison
We explore asynchronous unison in the presence of systemic transient and
permanent Byzantine faults in shared memory. We observe that the problem is not
solvable under less than strongly fair scheduler or for system topologies with
maximum node degree greater than two. We present a self-stabilizing
Byzantine-tolerant solution to asynchronous unison for chain and ring
topologies. Our algorithm has minimum possible containment radius and optimal
stabilization time
The concept and impact analysis of a flexible mobility on demand system
This paper introduces an innovative transportation concept called Flexible Mobility on
Demand (FMOD), which provides personalized services to passengers. FMOD is a demand
responsive system in which a list of travel options is provided in real-time to each passen-
ger request. The system provides passengers with flexibility to choose from a menu that is
optimized in an assortment optimization framework. For operators, there is flexibility in
terms of vehicle allocation to different service types: taxi, shared-taxi and mini-bus. The
allocation of the available fleet to these three services is carried out dynamically so that
vehicles can change roles during the day. The FMOD system is built based on a choice
model and consumer surplus is taken into account in order to improve passenger satisfac-
tion. Furthermore, profits of the operators are expected to increase since the system adapts
to changing demand patterns. In this paper, we introduce the concept of FMOD and present
preliminary simulation results. It is shown that the dynamic allocation of the vehicles to
different services provides significant benefits over static allocation. Furthermore, it is
observed that the trade-off between consumer surplus and operator’s profit is critical.
The optimization model is adapted in order to take into account this trade-off by control-
ling the level of passenger satisfaction. It is shown that with such control mechanisms
FMOD provides improved results in terms of both profit and consumer surplus
The Concept and Impact Analysis of a Flexible Mobility on Demand System
This paper introduces an innovative transportation concept called Flexible Mobility on Demand (FMOD), which provides personalized services to passengers. FMOD is a demand responsive system in which a list of travel options is provided in real-time to each passenger request. The system provides passengers with flexibility to choose from a menu that is
optimized in an assortment optimization framework. For operators, there is flexibility in terms of vehicle allocation to di erent service types: taxi, shared-taxi and mini-bus. The allocation of the available fleet to these three services is carried out dynamically and based on demand and supply so that vehicles can change roles during the day. The FMOD system is built based on a choice model and consumer surplus is taken into account in order to
improve the passenger satisfaction. Furthermore, pro fits of the operators are expected to increase since the system adapts to changing demand patterns. In this paper, we introduce the concept of FMOD and present preliminary simulation results that quantify the added value of this system.Fujitsu Laboratories funding under the OSP account 6925717
Fujitsu Laboratories funding under the OSP account 6927900
Fujitsu Laboratories funding under the OSP account 692960
A Taxonomy of Daemons in Self-stabilization
We survey existing scheduling hypotheses made in the literature in
self-stabilization, commonly referred to under the notion of daemon. We show
that four main characteristics (distribution, fairness, boundedness, and
enabledness) are enough to encapsulate the various differences presented in
existing work. Our naming scheme makes it easy to compare daemons of particular
classes, and to extend existing possibility or impossibility results to new
daemons. We further examine existing daemon transformer schemes and provide the
exact transformed characteristics of those transformers in our taxonomy.Comment: 26 page
Preferred lightness and chromatic image contrast reproduction
In this study, the image preference as a function of lightness and chromatic contrast of images produced on an ink-jet printer is examined. The purpose is to develop image manipulation rules, useful in the development of printer algorithms to produce images that are preferred by viewers over images that have been printed without application of these rules. Five images are used during the psychophysical experiment, two business graphics and three pictorial, processed in three different ways in RLAB color space, once having only the tightness contrast varied, then only the chromatic contrast, and finally both lightness and chromatic contrast varied. The results showed that for the graphics images seen without a CRT original used for comparison, the mean preference was an increase in lightness contrast, while with an original available for comparison, the mean preference indicated a decrease in both lightness and chromatic contrast. For pictorial images, in the first phase of the experiment the mean preference was an increase in both lightness and chromatic contrast, and after comparison, a decrease in lightness and simultaneous decrease in lightness and chromatic contrast are the most preferred
Fundamental Approaches to Software Engineering
computer software maintenance; computer software selection and evaluation; formal logic; formal methods; formal specification; programming languages; semantics; software engineering; specifications; verificatio