110,209 research outputs found
Requirements and Tools for Variability Management
Explicit and software-supported Business Process Management has become the core infrastructure of any medium and large organization that has a need to be efficient and effective. The number of processes of a single organization can be very high, furthermore, they might be very similar, be in need of momentary change, or evolve frequently. If the ad-hoc adaptation and customization of processes is currently the dominant way, it clearly is not the best. In fact, providing tools for supporting the explicit management of variation in processes (due to customization or evolution needs) has a profound impact on the overall life-cycle of processes in organizations. Additionally, with the increasing adoption of Service-Oriented Architectures, the infrastructure to support automatic reconfiguration and adaptation of business process is solid.
In this paper, after defining variability in business process management, we consider the requirements for explicit variation handling for (service based) business process systems. eGovernment serves as an illustrative example of reuse. In this case study, all local municipalities need to implement the same general legal process while adapting it to the local business practices and IT infrastructure needs. Finally, an evaluation of existing tools for explicit variability management is provided with respect to the requirements identified.
A Systematic Review of Tracing Solutions in Software Product Lines
Software Product Lines are large-scale, multi-unit systems that enable
massive, customized production. They consist of a base of reusable artifacts
and points of variation that provide the system with flexibility, allowing
generating customized products. However, maintaining a system with such
complexity and flexibility could be error prone and time consuming. Indeed, any
modification (addition, deletion or update) at the level of a product or an
artifact would impact other elements. It would therefore be interesting to
adopt an efficient and organized traceability solution to maintain the Software
Product Line. Still, traceability is not systematically implemented. It is
usually set up for specific constraints (e.g. certification requirements), but
abandoned in other situations. In order to draw a picture of the actual
conditions of traceability solutions in Software Product Lines context, we
decided to address a literature review. This review as well as its findings is
detailed in the present article.Comment: 22 pages, 9 figures, 7 table
Probabilistic prediction of rupture length, slip and seismic ground motions for an ongoing rupture: implications for early warning for large earthquakes
Earthquake EarlyWarning (EEW) predicts future ground shaking based on presently available
data. Long ruptures present the best opportunities for EEW since many heavily shaken areas
are distant from the earthquake epicentre and may receive long warning times. Predicting
the shaking from large earthquakes, however, requires some estimate of the likelihood of the
future evolution of an ongoing rupture. An EEW system that anticipates future rupture using
the present magnitude (or rupture length) together with the Gutenberg-Richter frequencysize
statistics will likely never predict a large earthquake, because of the rare occurrence of
âextreme eventsâ. However, it seems reasonable to assume that large slip amplitudes increase
the probability for evolving into a large earthquake. To investigate the relationship between the
slip and the eventual size of an ongoing rupture, we simulate suites of 1-D rupture series from
stochastic models of spatially heterogeneous slip. We find that while large slip amplitudes
increase the probability for the continuation of a rupture and the possible evolution into a
âBig Oneâ, the recognition that rupture is occurring on a spatially smooth fault has an even
stronger effect.We conclude that anEEWsystem for large earthquakes needs some mechanism
for the rapid recognition of the causative fault (e.g., from real-time GPS measurements) and
consideration of its âsmoothnessâ. An EEW system for large earthquakes on smooth faults,
such as the San Andreas Fault, could be implemented in two ways: the system could issue
a warning, whenever slip on the fault exceeds a few metres, because the probability for a
large earthquake is high and strong shaking is expected to occur in large areas around the
fault. A more sophisticated EEW system could use the present slip on the fault to estimate the
future slip evolution and final rupture dimensions, and (using this information) could provide
probabilistic predictions of seismic ground motions along the evolving rupture. The decision
on whether an EEW system should be realized in the first or in the second way (or in a
combination of both) is user-specific
Self-adaptive exploration in evolutionary search
We address a primary question of computational as well as biological research
on evolution: How can an exploration strategy adapt in such a way as to exploit
the information gained about the problem at hand? We first introduce an
integrated formalism of evolutionary search which provides a unified view on
different specific approaches. On this basis we discuss the implications of
indirect modeling (via a ``genotype-phenotype mapping'') on the exploration
strategy. Notions such as modularity, pleiotropy and functional phenotypic
complex are discussed as implications. Then, rigorously reflecting the notion
of self-adaptability, we introduce a new definition that captures
self-adaptability of exploration: different genotypes that map to the same
phenotype may represent (also topologically) different exploration strategies;
self-adaptability requires a variation of exploration strategies along such a
``neutral space''. By this definition, the concept of neutrality becomes a
central concern of this paper. Finally, we present examples of these concepts:
For a specific grammar-type encoding, we observe a large variability of
exploration strategies for a fixed phenotype, and a self-adaptive drift towards
short representations with highly structured exploration strategy that matches
the ``problem's structure''.Comment: 24 pages, 5 figure
Accretion and ejection in black-hole X-ray transients
Aims: We summarize the current observational picture of the outbursts of
black-hole X-ray transients (BHTs), based on the evolution traced in a
hardness-luminosity diagram (HLD), and we offer a physical interpretation.
Methods: The basic ingredient in our interpretation is the Poynting-Robertson
Cosmic Battery (PRCB, Contopoulos & Kazanas 1998), which provides locally the
poloidal magnetic field needed for the ejection of the jet. In addition, we
make two assumptions, easily justifiable. The first is that the mass-accretion
rate to the black hole in a BHT outburst has a generic bell-shaped form. This
is guaranteed by the observational fact that all BHTs start their outburst and
end it at the quiescent state. The second assumption is that at low accretion
rates the accretion flow is geometrically thick, ADAF-like, while at high
accretion rates it is geometrically thin.
Results: Both, at the beginning and the end of an outburst, the PRCB
establishes a strong poloidal magnetic field in the ADAF-like part of the
accretion flow, and this explains naturally why a jet is always present in the
right part of the HLD. In the left part of the HLD, the accretion flow is in
the form of a thin disk, and such a disk cannot sustain a strong poloidal
magnetic filed. Thus, no jet is expected in this part of the HLD. The
counterclockwise traversal of the HLD is explained as follows: the poloidal
magnetic field in the ADAF forces the flow to remain ADAF and the source to
move upwards in the HLD rather than to turn left. Thus, the history of the
system determines the counterclockwise traversal of the HLD. As a result, no
BHT is expected to ever traverse the entire HLD curve in the clockwise
direction.
Conclusions: We offer a physical interpretation of accretion and ejection in
BHTs with only one parameter, the mass transfer rate.Comment: Accepted for publication in A&
Level and length of cyclic solar activity during the Maunder minimum as deduced from the active day statistics
The Maunder minimum (MM) of greatly reduced solar activity took place in
1645-1715, but the exact level of sunspot activity is uncertain as based, to a
large extent, on historical generic statements of the absence of spots on the
Sun. Here we aim, using a conservative approach, to assess the level and length
of solar cycle during the Maunder minimum, on the basis of direct historical
records by astronomers of that time. A database of the active and inactive days
(days with and without recorded sunspots on the solar disc respectively) is
constructed for three models of different levels of conservatism (loose ML,
optimum MO and strict MS models) regarding generic no-spot records. We have
used the active day fraction to estimate the group sunspot number during the
MM. A clear cyclic variability is found throughout the MM with peaks at around
1655--1657, 1675, 1684 and 1705, and possibly 1666, with the active day
fraction not exceeding 0.2, 0.3 or 0.4 during the core MM, for the three
models. Estimated sunspot numbers are found very low in accordance with a grand
minimum of solar activity.
We have found, for the core MM (1650-1700), that: (1) A large fraction of
no-spot records, corresponding to the solar meridian observations, may be
unreliable in the conventional database. (2) The active day fraction remained
low (below 0.3-0.4) throughout the MM, indicating the low level of sunspot
activity. (3) The solar cycle appears clearly during the core MM. (4) The
length of the solar cycle during the core MM appears years, but there
is an uncertainty in that. (5) The magnitude of the sunspot cycle during MM is
assessed to be below 5-10 in sunspot numbers;
A hypothesis of the high solar cycles during the MM is not confirmed.Comment: Accepted to Astron. Astrophy
From physics to biology by extending criticality and symmetry breakings
Symmetries play a major role in physics, in particular since the work by E. Noether and H. Weyl in the first half of last century. Herein, we briefly review their role by recalling how symmetry changes allow to conceptually move from classical to relativistic and quantum physics. We then introduce our ongoing theoretical analysis in biology and show that symmetries play a radically different role in this discipline, when compared to those in current physics. By this comparison, we stress that symmetries must be understood in relation to conservation and stability properties, as represented in the theories. We posit that the dynamics of biological organisms, in their various levels of organization, are not just processes, but permanent (extended, in our terminology) critical transitions and, thus, symmetry changes. Within the limits of a relative structural stability (or interval of viability), variability is at the core of these transitions
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