84,205 research outputs found
The effect of metapopulation processes on the spatial scale of adaptation across an environmental gradient
We show that the butterfly Aricia agestis (Lycaenidae) is adapted to its
thermal environment in via integer changes in the numbers of generations per year
(voltinism): it has two generations per year in warm habitats and one generation per
year in cool habitats in north Wales (UK). Voltinism is an âadaptive peakâ since
individuals having an intermediate number of generations per year would fail to
survive the winter, and indeed no populations showed both voltinism types in nature.
In spite of this general pattern, 11% of populations apparently possess the âwrongâ
voltinism for their local environment, and population densities were lower in thermally
intermediate habitat patches. Population dynamic data and patterns of genetic
differentiation suggest that adaptation occurs at the metapopulation level, with local
populations possessing the voltinism type appropriate for the commonest habitat type
within each population network. When populations and groups of populations go
extinct, they tend to be replaced by colonists from the commonest thermal environment
nearby, even if this is the locally incorrect adaptation. Our results illustrate how
stochastic population turnover can impose a limit on local adaptation over distances
many times larger than predicted on the basis of normal dispersal movements
Open Programming Language Interpreters
Context: This paper presents the concept of open programming language
interpreters and the implementation of a framework-level metaobject protocol
(MOP) to support them. Inquiry: We address the problem of dynamic interpreter
adaptation to tailor the interpreter's behavior on the task to be solved and to
introduce new features to fulfill unforeseen requirements. Many languages
provide a MOP that to some degree supports reflection. However, MOPs are
typically language-specific, their reflective functionality is often
restricted, and the adaptation and application logic are often mixed which
hardens the understanding and maintenance of the source code. Our system
overcomes these limitations. Approach: We designed and implemented a system to
support open programming language interpreters. The prototype implementation is
integrated in the Neverlang framework. The system exposes the structure,
behavior and the runtime state of any Neverlang-based interpreter with the
ability to modify it. Knowledge: Our system provides a complete control over
interpreter's structure, behavior and its runtime state. The approach is
applicable to every Neverlang-based interpreter. Adaptation code can
potentially be reused across different language implementations. Grounding:
Having a prototype implementation we focused on feasibility evaluation. The
paper shows that our approach well addresses problems commonly found in the
research literature. We have a demonstrative video and examples that illustrate
our approach on dynamic software adaptation, aspect-oriented programming,
debugging and context-aware interpreters. Importance: To our knowledge, our
paper presents the first reflective approach targeting a general framework for
language development. Our system provides full reflective support for free to
any Neverlang-based interpreter. We are not aware of any prior application of
open implementations to programming language interpreters in the sense defined
in this paper. Rather than substituting other approaches, we believe our system
can be used as a complementary technique in situations where other approaches
present serious limitations
Learning in evolutionary environments
Not availabl
An active-architecture approach to COTS integration
Commercial off-the-shelf (COTS) software products are increasingly used as standard components within integrated information systems. This creates challenges since both their developers and source code are not usually available, and the ongoing development of COTS cannot be predicted. The ArchWare Framework approach recognises COTS products as part of the ambient environment of an information system and therefore an important part of development is incorporating COTS as effective system components. This integration of COTS components, and the composition of components, is captured by an active architecture model which changes as the system evolves. Indeed the architecture modelling language used enables it to express the monitoring and evolution of a system. This active architecture model is structured using control system principles. By modelling both integration and evolution it can guide the systemâs response to both predicted and emergent changes that arise from the use of COTS products.Publisher PDFPeer reviewe
Fine Grained Component Engineering of Adaptive Overlays: Experiences and Perspectives
Recent years have seen significant research being carried out into peer-to-peer (P2P) systems. This work has focused on the styles and applications of P2P computing, from grid computation to content distribution; however, little investigation has been performed into how these systems are built. Component based engineering is an approach that has seen successful deployment in the field of middleware development; functionality is encapsulated in âbuilding blocksâ that can be dynamically plugged together to form complete systems. This allows efficient, flexible and adaptable systems to be built with lower overhead and development complexity. This paper presents an investigation into the potential of using component based engineering in the design and construction of peer-to-peer overlays. It is highlighted that the quality of these properties is dictated by the component architecture used to implement the system. Three reusable decomposition architectures are designed and evaluated using Chord and Pastry case studies. These demonstrate that significant improvements can be made over traditional design approaches resulting in much more reusable, (re)configurable and extensible systems
A Model of Emotion as Patterned Metacontrol
Adaptive systems use feedback as a key strategy to cope with uncertainty and change in their environments. The information fed back from the sensorimotor loop into the control architecture can be used to change different elements of the controller at four different levels: parameters of the control model, the control model itself, the functional organization of the agent and the functional components of the agent. The complexity of such a space of potential conïŹgurations is daunting. The only viable alternative for the agent ?in practical, economical, evolutionary terms? is the reduction of the dimensionality of the conïŹguration space. This reduction is achieved both by functionalisation âor, to be more precise, by interface minimizationâ and by patterning, i.e. the selection among a predeïŹned set of organisational conïŹgurations. This last analysis let us state the central problem of how autonomy emerges from the integration of the cognitive, emotional and autonomic systems in strict functional terms: autonomy is achieved by the closure of functional dependency. In this paper we will show a general model of how the emotional biological systems operate following this theoretical analysis and how this model is also of applicability to a wide spectrum of artiïŹcial systems
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