1,965 research outputs found
Composable entropy and deviation from macroscopic equilibrium
We formulate, under general conditions, the problem of maximisation of the
total entropy of the system, assumed to be in a composable form, for fixed
total value of the constrained quantity. We derive the general form of the
composability function and also point out the criterion which leads to a
violation of the zeroth law of thermodynamics.Comment: 10 pages, Latex, no figure
An Analysis of Composability and Composition Anomalies
The separation of concerns principle aims at decomposing a given design problem into concerns that are mapped to multiple independent software modules. The application of this principle eases the composition of the concerns and as such supports composability. Unfortunately, a clean separation (and composition of concerns) at the design level does not always imply the composability of the concerns at the implementation level. The composability might be reduced due to limitations of the implementation abstractions and composition mechanisms. The paper introduces the notion of composition anomaly to describe a general set of unexpected composition problems that arise when mapping design concerns to implementation concerns. To distinguish composition anomalies from other composition problems the requirements for composability at the design level is provided. The ideas are illustrated for a distributed newsgroup system
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
Omphale: Streamlining the Communication for Jobs in a Multi Processor System on Chip
Our Multi Processor System on Chip (MPSoC) template provides processing tiles that are connected via a network on chip. A processing tile contains a processing unit and a Scratch Pad Memory (SPM). This paper presents the Omphale tool that performs the first step in mapping a job, represented by a task graph, to such an MPSoC, given the SPM sizes as constraints. Furthermore a memory tile is introduced. The result of Omphale is a Cyclo Static DataFlow (CSDF) model and a task graph where tasks communicate via sliding windows that are located in circular buffers. The CSDF model is used to determine the size of the buffers and the communication pattern of the data. A buffer must fit in the SPM of the processing unit that is reading from it, such that low latency access is realized with a minimized number of stall cycles. If a task and its buffer exceed the size of the SPM, the task is examined for additional parallelism or the circular buffer is partly located in a memory tile. This results in an extended task graph that satisfies the SPM size constraints
Designing Software Architectures As a Composition of Specializations of Knowledge Domains
This paper summarizes our experimental research and software development activities in designing robust, adaptable and reusable software architectures. Several years ago, based on our previous experiences in object-oriented software development, we made the following assumption: ‘A software architecture should be a composition of specializations of knowledge domains’. To verify this assumption we carried out three pilot projects. In addition to the application of some popular domain analysis techniques such as use cases, we identified the invariant compositional structures of the software architectures and the related knowledge domains. Knowledge domains define the boundaries of the adaptability and reusability capabilities of software systems. Next, knowledge domains were mapped to object-oriented concepts. We experienced that some aspects of knowledge could not be directly modeled in terms of object-oriented concepts. In this paper we describe our approach, the pilot projects, the experienced problems and the adopted solutions for realizing the software architectures. We conclude the paper with the lessons that we learned from this experience
Secure bit commitment from relativistic constraints
We investigate two-party cryptographic protocols that are secure under
assumptions motivated by physics, namely relativistic assumptions
(no-signalling) and quantum mechanics. In particular, we discuss the security
of bit commitment in so-called split models, i.e. models in which at least some
of the parties are not allowed to communicate during certain phases of the
protocol. We find the minimal splits that are necessary to evade the
Mayers-Lo-Chau no-go argument and present protocols that achieve security in
these split models. Furthermore, we introduce the notion of local versus global
command, a subtle issue that arises when the split committer is required to
delegate non-communicating agents to open the commitment. We argue that
classical protocols are insecure under global command in the split model we
consider. On the other hand, we provide a rigorous security proof in the global
command model for Kent's quantum protocol [Kent 2011, Unconditionally Secure
Bit Commitment by Transmitting Measurement Outcomes]. The proof employs two
fundamental principles of modern physics, the no-signalling property of
relativity and the uncertainty principle of quantum mechanics.Comment: published version, IEEE format, 18 pages, 8 figure
Multilevel Contracts for Trusted Components
This article contributes to the design and the verification of trusted
components and services. The contracts are declined at several levels to cover
then different facets, such as component consistency, compatibility or
correctness. The article introduces multilevel contracts and a
design+verification process for handling and analysing these contracts in
component models. The approach is implemented with the COSTO platform that
supports the Kmelia component model. A case study illustrates the overall
approach.Comment: In Proceedings WCSI 2010, arXiv:1010.233
Concepts of quantum non-Markovianity: a hierarchy
Markovian approximation is a widely-employed idea in descriptions of the
dynamics of open quantum systems (OQSs). Although it is usually claimed to be a
concept inspired by classical Markovianity, the term quantum Markovianity is
used inconsistently and often unrigorously in the literature. In this report we
compare the descriptions of classical stochastic processes and quantum
stochastic processes (as arising in OQSs), and show that there are inherent
differences that lead to the non-trivial problem of characterizing quantum
non-Markovianity. Rather than proposing a single definition of quantum
Markovianity, we study a host of Markov-related concepts in the quantum regime.
Some of these concepts have long been used in quantum theory, such as quantum
white noise, factorization approximation, divisibility, Lindblad master
equation, etc.. Others are first proposed in this report, including those we
call past-future independence, no (quantum) information backflow, and
composability. All of these concepts are defined under a unified framework,
which allows us to rigorously build hierarchy relations among them. With
various examples, we argue that the current most often used definitions of
quantum Markovianity in the literature do not fully capture the memoryless
property of OQSs. In fact, quantum non-Markovianity is highly
context-dependent. The results in this report, summarized as a hierarchy
figure, bring clarity to the nature of quantum non-Markovianity.Comment: Clarifications and references added; discussion of the related
classical hierarchy significantly improved. To appear in Physics Report
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