216,210 research outputs found
Denotational Linear Time Semantics and Sequential Composition
This paper focuses on the issue of modelling sequential composition in denotational linear time semantics for (nondeterministic) languages which admit infinite computations. This operator deserves special attention as it causes problems to meet the requirements of a standard denotational semantics based on metric or cpo. We present a general framework for the treatment of sequential composition. It turns out that a program can be described by its maximal computations in the metric approach whereas the partial order approach is suitable to describe a program by all its partial computations
Schr\"odinger-Feynman quantization and composition of observables in general boundary quantum field theory
We show that the Feynman path integral together with the Schr\"odinger
representation gives rise to a rigorous and functorial quantization scheme for
linear and affine field theories. Since our target framework is the general
boundary formulation, the class of field theories that can be quantized in this
way includes theories without a metric spacetime background. We also show that
this quantization scheme is equivalent to a holomorphic quantization scheme
proposed earlier and based on geometric quantization. We proceed to include
observables into the scheme, quantized also through the path integral. We show
that the quantized observables satisfy the canonical commutation relations, a
feature shared with other quantization schemes also discussed. However, in
contrast to other schemes the presented quantization also satisfies a
correspondence between the composition of classical observables through their
product and the composition of their quantized counterparts through spacetime
gluing. In the special case of quantum field theory in Minkowski space this
reproduces the operationally correct composition of observables encoded in the
time-ordered product. We show that the quantization scheme also generalizes
other features of quantum field theory such as the generating function of the
S-matrix.Comment: 47 pages, LaTeX + AMS; v2: minor corrections, references update
A Framework for the Evaluation of Semantics-based Service Composition Approaches
The benefits of service composition are being largely acknowledged in the literature nowadays. However, as the amount of available services increases, it becomes difficult to manage, discover, select and compose them, so that automation is required in these processes. This can be achieved by using semantic information represented in ontologies. Currently there are many different approaches that support semantics-based service composition. However, still little effort has been spent on creating a common methodology to evaluate and compare such approaches. In this paper we present our initial ideas to create an evaluation framework for semantics-based service composition approaches. We use a collection of existing services, and define a set of evaluation metrics, confusion matrix-based and time-based. Furthermore, we present how composition evaluation scenarios are generated from the collection of services and specify the strategy to be used in the evaluation process. We demonstrate the proposed framework through an example. Currently there are mechanisms and initiatives to address the evaluation of the semantics-based service discovery and matchmaking approaches. However, still few efforts have been spent on the creation of comprehensive evaluation mechanisms for semantics-based service composition approaches
On the fate of Lorentz symmetry in relative-locality momentum spaces
The most studied doubly-special-relativity scenarios, theories with both the
speed-of-light scale and a length/inverse-momentum scale as non-trivial
relativistic invariants, have concerned the possibility of enforcing
relativistically some nonlinear laws on momentum space. For the
"relative-locality framework" recently proposed in arXiv:1101.0931 a central
role is played by nonlinear laws on momentum space, with the guiding principle
that they should provide a characterization of the geometry of momentum space.
Building on previous doubly-special-relativity results I here identify a
criterion for establishing whether or not a given geometry of the
relative-locality momentum space is "DSR compatible", i.e. compatible with an
observer-independent formulation of theories on that momentum space. I find
that given some chosen parametrization of momentum-space geometry the criterion
takes the form of an elementary algorithm. I show that relative-locality
momentum spaces that fail my criterion definitely "break" Lorentz invariance,
i.e. theories on such momentum spaces necessarily are observer-dependent
"ether" theories. By working out a few examples I provide evidence that when
the criterion is instead satisfied one does manage to produce a relativistic
formulation. The examples I use to illustrate the applicability of my criterion
also have some intrinsic interest, including two particularly noteworthy cases
of -Poincar\'e-inspired momentum spaces.Comment: 24 pages, LaTe
Ensuring Cyber-Security in Smart Railway Surveillance with SHIELD
Modern railways feature increasingly complex embedded computing systems for surveillance, that are moving towards fully wireless smart-sensors. Those systems are aimed at monitoring system status from a physical-security viewpoint, in order to detect intrusions and other environmental anomalies. However, the same systems used for physical-security surveillance are vulnerable to cyber-security threats, since they feature distributed hardware and software architectures often interconnected by ‘open networks’, like wireless channels and the Internet. In this paper, we show how the integrated approach to Security, Privacy and Dependability (SPD) in embedded systems provided by the SHIELD framework (developed within the EU funded pSHIELD and nSHIELD research projects) can be applied to railway surveillance systems in order to measure and improve their SPD level. SHIELD implements a layered architecture (node, network, middleware and overlay) and orchestrates SPD mechanisms based on ontology models, appropriate metrics and composability. The results of prototypical application to a real-world demonstrator show the effectiveness of SHIELD and justify its practical applicability in industrial settings
Attack-Surface Metrics, OSSTMM and Common Criteria Based Approach to “Composable Security” in Complex Systems
In recent studies on Complex Systems and Systems-of-Systems theory, a huge effort has been put to cope with behavioral problems, i.e. the possibility of controlling a desired overall or end-to-end behavior by acting on the individual elements that constitute the system itself. This problem is particularly important in the “SMART” environments, where the huge number of devices, their significant computational capabilities as well as their tight interconnection produce a complex architecture for which it is difficult to predict (and control) a desired behavior; furthermore, if the scenario is allowed to dynamically evolve through the modification of both topology and subsystems composition, then the control problem becomes a real challenge. In this perspective, the purpose of this paper is to cope with a specific class of control problems in complex systems, the “composability of security functionalities”, recently introduced by the European Funded research through the pSHIELD and nSHIELD projects (ARTEMIS-JU programme). In a nutshell, the objective of this research is to define a control framework that, given a target security level for a specific application scenario, is able to i) discover the system elements, ii) quantify the security level of each element as well as its contribution to the security of the overall system, and iii) compute the control action to be applied on such elements to reach the security target. The main innovations proposed by the authors are: i) the definition of a comprehensive methodology to quantify the security of a generic system independently from the technology and the environment and ii) the integration of the derived metrics into a closed-loop scheme that allows real-time control of the system. The solution described in this work moves from the proof-of-concepts performed in the early phase of the pSHIELD research and enrich es it through an innovative metric with a sound foundation, able to potentially cope with any kind of pplication scenarios (railways, automotive, manufacturing, ...)
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