328,584 research outputs found
Toward an Algebraic Theory of Systems
We propose the concept of a system algebra with a parallel composition
operation and an interface connection operation, and formalize
composition-order invariance, which postulates that the order of composing and
connecting systems is irrelevant, a generalized form of associativity.
Composition-order invariance explicitly captures a common property that is
implicit in any context where one can draw a figure (hiding the drawing order)
of several connected systems, which appears in many scientific contexts. This
abstract algebra captures settings where one is interested in the behavior of a
composed system in an environment and wants to abstract away anything internal
not relevant for the behavior. This may include physical systems, electronic
circuits, or interacting distributed systems.
One specific such setting, of special interest in computer science, are
functional system algebras, which capture, in the most general sense, any type
of system that takes inputs and produces outputs depending on the inputs, and
where the output of a system can be the input to another system. The behavior
of such a system is uniquely determined by the function mapping inputs to
outputs. We consider several instantiations of this very general concept. In
particular, we show that Kahn networks form a functional system algebra and
prove their composition-order invariance.
Moreover, we define a functional system algebra of causal systems,
characterized by the property that inputs can only influence future outputs,
where an abstract partial order relation captures the notion of "later". This
system algebra is also shown to be composition-order invariant and appropriate
instantiations thereof allow to model and analyze systems that depend on time
Nanoscale Networks of Metal Oxides by Polymer Imprinting and Templating for Future Adaptable Electronics
While network formation is prevalent in nature, networks are generally not expected in inorganic structures. Exceptions are those cases in which surface states become important, such as nanoparticles. However, even in these cases, the morphology of these networks is difficult to control and they show a large degree of disorder. In this work, we show that highly ordered and interconnected nanoscale networks of functional metal oxides can be fabricated by a combination of polymer imprinting and polymer templating through solution processable methods. We report the fabrication of a number of functional oxide networks (i.e., BiFeO3, SrTiO3, La0.7Ca0.3MnO3, and HfO2) from solution, showing that all the oxide materials tried so far are able to follow the self-assembled network morphology dictated by the polymer structure. These networks were characterized for the overall structure by scanning electron microscopy and atomic force microscopy (AFM). Grazing incidence small angle X-ray scattering showed a good imprint quality on the mm2 scale for the combined networks, which is challenging given that multiple processing steps were involved during the fabrication. The material stoichiometries were investigated by X-ray photoemission spectroscopy and the crystal phases by grazing incidence wide angle X-ray scattering. When electronic functionality is anticipated, the networks behave as expected: conducting AFM on the La0.7Ca0.3MnO3 networks confirmed the conductive character of this composition; and piezoresponse force microscopy of the BiFeO3 network is consistent with the presence of ferroelectric behavior. These nanoscale networks show promise for future applications in adaptable electronics, such as neuromorphic computing or brain-inspired information processing.</p
S+Net: extending functional coordination with extra-functional semantics
This technical report introduces S+Net, a compositional coordination language
for streaming networks with extra-functional semantics. Compositionality
simplifies the specification of complex parallel and distributed applications;
extra-functional semantics allow the application designer to reason about and
control resource usage, performance and fault handling. The key feature of
S+Net is that functional and extra-functional semantics are defined
orthogonally from each other. S+Net can be seen as a simultaneous
simplification and extension of the existing coordination language S-Net, that
gives control of extra-functional behavior to the S-Net programmer. S+Net can
also be seen as a transitional research step between S-Net and AstraKahn,
another coordination language currently being designed at the University of
Hertfordshire. In contrast with AstraKahn which constitutes a re-design from
the ground up, S+Net preserves the basic operational semantics of S-Net and
thus provides an incremental introduction of extra-functional control in an
existing language.Comment: 34 pages, 11 figures, 3 table
Design of an autonomous software platform for future symbiotic service management
Nowadays, public as well as private communication infrastructures are all contending for the same limited amount of bandwidth. To optimally share network resources, symbiotic networks have been proposed, which cross logical and physical boundaries to improve the reliability, scalability, and energy efficiency of the network as a whole as well as its constituents. This paper focuses on software services in such symbiotic networks. We propose a platform for the intelligent composition of services provided by symbiotically connected parties, resulting in novel cooperation opportunities. The platform harvests Semantic Web technology to describe services in a highly expressive manner, and constructs service compositions using SeCoA, our tunable best-first search algorithm. The resulting compositions are then enacted via CaPI, a reconfigurable middleware infrastructure. By means of an illustrative scenario, we provide further insight into the platform's functioning
Inter-organizational fault management: Functional and organizational core aspects of management architectures
Outsourcing -- successful, and sometimes painful -- has become one of the
hottest topics in IT service management discussions over the past decade. IT
services are outsourced to external service provider in order to reduce the
effort required for and overhead of delivering these services within the own
organization. More recently also IT services providers themselves started to
either outsource service parts or to deliver those services in a
non-hierarchical cooperation with other providers. Splitting a service into
several service parts is a non-trivial task as they have to be implemented,
operated, and maintained by different providers. One key aspect of such
inter-organizational cooperation is fault management, because it is crucial to
locate and solve problems, which reduce the quality of service, quickly and
reliably. In this article we present the results of a thorough use case based
requirements analysis for an architecture for inter-organizational fault
management (ioFMA). Furthermore, a concept of the organizational respective
functional model of the ioFMA is given.Comment: International Journal of Computer Networks & Communications (IJCNC
A design model for Open Distributed Processing systems
This paper proposes design concepts that allow the conception, understanding and development of complex technical structures for open distributed systems. The proposed concepts are related to, and partially motivated by, the present work on Open Distributed Processing (ODP). As opposed to the current ODP approach, the concepts are aimed at supporting a design trajectory with several, related abstraction levels. Simple examples are used to illustrate the proposed concepts
S-Net for multi-memory multicores
Copyright ACM, 2010. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in Proceedings of the 5th ACM SIGPLAN Workshop on Declarative Aspects of Multicore Programming: http://doi.acm.org/10.1145/1708046.1708054S-Net is a declarative coordination language and component technology aimed at modern multi-core/many-core architectures and systems-on-chip. It builds on the concept of stream processing to structure dynamically evolving networks of communicating asynchronous components. Components themselves are implemented using a conventional language suitable for the application domain. This two-level software architecture maintains a familiar sequential development environment for large parts of an application and offers a high-level declarative approach to component coordination. In this paper we present a conservative language extension for the placement of components and component networks in a multi-memory environment, i.e. architectures that associate individual compute cores or groups thereof with private memories. We describe a novel distributed runtime system layer that complements our existing multithreaded runtime system for shared memory multicores. Particular emphasis is put on efficient management of data communication. Last not least, we present preliminary experimental data
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